Tech Dictionary

Last Updated: October 24, 2025

Navigate the complex world of email hosting, domains, and web services with our comprehensive technical dictionary. From A to Z, we explain the terminology, acronyms, and concepts you'll encounter.

A

A Record

Definition: DNS record that maps a domain name to an IPv4 address.

Example: example.com → 192.0.2.1

Use Case: Points your domain to your web server's IP address.

Related Terms: AAAA Record, DNS, IP Address

AAAA Record (Quad-A)

Definition: DNS record that maps a domain name to an IPv6 address.

Example: example.com → 2001:0db8:85a3::8a2e:0370:7334

Use Case: Modern alternative to A records for IPv6 infrastructure.

Related Terms: A Record, IPv6, DNS

Alias

Definition: Alternative name or address that points to a primary resource.

Example: info@company.com → redirects to → support@company.com

Use Case: Create multiple email addresses routing to same mailbox.

Related Terms: Email Alias, CNAME, Forwarding

API (Application Programming Interface)

Definition: Set of protocols allowing different software applications to communicate.

Example: Using email API to send automated messages from your application.

Use Case: Integrate email services into your custom applications.

Related Terms: REST API, Webhook, Integration

Attachment

Definition: File sent along with an email message.

Common Types: Documents (.pdf, .docx), images (.jpg, .png), archives (.zip)

Size Limits: Typically 25-50 MB per email

Best Practice: Use cloud storage links for large files.

Related Terms: MIME, Base64, Email Client

Auth Code (Authorization Code)

Definition: Unique password required to transfer a domain between registrars.

Also Called: EPP Code, Transfer Key, Domain Password

Format: 10-20 character alphanumeric string

Security: Keep confidential, regenerate if compromised.

Related Terms: Domain Transfer, EPP, Registrar

Auto-Responder

Definition: Automated email reply sent in response to incoming messages.

Use Cases:

• Out-of-office notifications
• Confirmation messages
• Welcome emails
• Support ticket acknowledgments

Best Practice: Include alternative contact information.

Related Terms: Vacation Message, Automated Reply

B

Bandwidth

Definition: Amount of data that can be transmitted over an internet connection in a given time.

Measurement: Usually in Mbps (megabits per second) or GB/month

Use Case: Determines how fast your website loads and how much traffic it can handle.

Related Terms: Data Transfer, Throughput, Network Speed

Blacklist (Blocklist)

Definition: List of IP addresses or domains identified as sources of spam.

Impact: Emails from blacklisted sources are blocked or marked as spam.

Common Lists:

• Spamhaus
• SORBS
• SpamCop
• Barracuda

How to Check: Use blacklist checker tools like MXToolbox.

Removal: Contact the blacklist organization with proof of resolution.

Related Terms: Spam, Reputation, Deliverability

BCC (Blind Carbon Copy)

Definition: Email recipients hidden from other recipients.

Use Case: Send to multiple people without revealing addresses to each other.

Privacy: Recipients in BCC cannot see each other's addresses.

Best Practice: Use BCC for bulk emails to protect privacy.

Related Terms: CC, Email Header, Recipients

Bounce

Definition: Email that cannot be delivered and is returned to sender.

Types:

Hard Bounce:

• Permanent failure
• Invalid email address
• Domain doesn't exist
• Remove from list immediately

Soft Bounce:

• Temporary failure
• Mailbox full
• Server temporarily down
• Try again later

Bounce Rate: Percentage of emails that bounce (keep under 2%).

Related Terms: Deliverability, NDR, SMTP

Bounce Rate

Definition: Percentage of sent emails that are returned as undeliverable.

Calculation: (Bounced emails / Total sent emails) × 100

Acceptable Rate: Under 2% (industry standard)

High Rate Impact:

• Damages sender reputation
• May trigger spam filters
• Can lead to blacklisting

Related Terms: Bounce, Deliverability, Email Metrics

C

CAA Record (Certification Authority Authorization)

Definition: DNS record specifying which Certificate Authorities can issue SSL certificates for your domain.

Example: example.com CAA 0 issue "letsencrypt.org"

Security Benefit: Prevents unauthorized SSL certificate issuance.

Use Case: Protect against certificate mis-issuance and fraud.

Related Terms: SSL, TLS, DNS, Security

Cache

Definition: Temporary storage of data for faster access.

Types:

• Browser Cache: Stores website files locally
• DNS Cache: Stores DNS lookup results
• Server Cache: Stores frequently accessed data

Benefit: Faster load times and reduced server load.

Clearing Cache: Often needed after website updates.

Related Terms: TTL, CDN, Performance

Catch-All Email

Definition: Email account that receives all messages sent to non-existent addresses at your domain.

Example: Email to anyname@company.com → goes to catch-all mailbox

Pros:

• Never miss an email due to typos
• Flexible addressing

Cons:

• Receives lots of spam
• Difficult to manage

Best Practice: Use with good spam filtering.

Related Terms: Email Forwarding, Mailbox, Wildcard

CC (Carbon Copy)

Definition: Email recipients who receive a copy; visible to all recipients.

Use Case: Keep others informed about email conversation.

Visibility: All recipients can see CC addresses.

Etiquette: Only CC people who need to know.

Related Terms: BCC, Email Header, Recipients

ccTLD (Country Code Top-Level Domain)

Definition: Two-letter top-level domain representing a specific country or territory.

Examples:

• .us - United States
• .uk - United Kingdom
• .ca - Canada
• .de - Germany
• .jp - Japan
• .au - Australia

Use Case: Target specific geographic markets or comply with local regulations.

Requirements: Some require local presence or documentation.

Related Terms: TLD, gTLD, Domain Extension

CDN (Content Delivery Network)

Definition: Network of distributed servers that deliver web content based on user's geographic location.

Popular Providers:

• Cloudflare
• CloudFront (AWS)
• Akamai
• Fastly

Benefits:

• Faster page load times
• Reduced server load
• Better performance globally
• DDoS protection

How It Works: Caches content on servers worldwide, serves from nearest location.

Related Terms: Cache, Performance, Edge Server

CNAME Record (Canonical Name)

Definition: DNS record that creates an alias pointing one domain to another domain.

Example: www.example.com → example.com

Use Case:

• Point www to root domain
• Configure CDN
• Alias subdomains

Restriction: Cannot be used for root domain (@).

Related Terms: A Record, DNS, Alias

CPanel

Definition: Popular web-based hosting control panel.

Features:

• File management
• Email account creation
• Database management
• DNS settings
• Security tools

Use Case: User-friendly interface for managing hosting.

Alternatives: Plesk, DirectAdmin, Custom panels

Related Terms: Control Panel, Web Hosting, Server Management

CPU (Central Processing Unit)

Definition: The "brain" of a server that processes instructions.

Measurement: GHz (gigahertz) and core count

Impact: Affects how fast your applications run.

Use Case: More CPU power needed for complex applications.

Related Terms: Server Resources, Performance, Hosting

D

Database

Definition: Organized collection of structured data stored electronically.

Common Types:

• MySQL: Popular relational database
• PostgreSQL: Advanced open-source database
• MongoDB: NoSQL document database
• MariaDB: MySQL fork

Use Case: Store website content, user data, application information.

Related Terms: SQL, Query, Table, Backend

DKIM (DomainKeys Identified Mail)

Definition: Email authentication method using cryptographic signatures.

How It Works:

1. Sender adds digital signature to email header
2. Signature created using private key
3. Recipient verifies using public key in DNS
4. Confirms email wasn't altered in transit

DNS Record Example:

default._domainkey.example.com TXT
"v=DKIM1; k=rsa; p=MIGfMA0GCSqGSIb3DQEBAQUAA..."

Benefits:

• Proves email authenticity
• Prevents email tampering
• Improves deliverability

Related Terms: SPF, DMARC, Email Authentication

DMARC (Domain-based Message Authentication, Reporting & Conformance)

Definition: Email authentication protocol that builds on SPF and DKIM.

DNS Record Example:

_dmarc.example.com TXT
"v=DMARC1; p=quarantine; rua=mailto:dmarc@example.com"

Policies:

• None: Monitor only, no action
• Quarantine: Mark suspicious emails as spam
• Reject: Block unauthenticated emails

Benefits:

• Prevents email spoofing
• Provides reporting
• Protects brand reputation

Related Terms: SPF, DKIM, Email Security

DNS (Domain Name System)

Definition: Internet's "phone book" that translates domain names to IP addresses.

How It Works:

User types: www.example.com
↓
DNS lookup: Finds IP address
↓
Returns: 192.0.2.1
↓
Browser connects to server

Record Types: A, AAAA, MX, CNAME, TXT, NS, SRV

Propagation: Time for DNS changes to spread globally (5 min - 48 hours).

Related Terms: Nameserver, DNS Records, Resolution

DNS Propagation

Definition: Time required for DNS changes to update across all DNS servers worldwide.

Typical Duration: 5 minutes to 48 hours (usually 1-4 hours)

Factors Affecting Speed:

• TTL (Time to Live) values
• ISP caching policies
• Geographic location
• DNS provider

Check Status: Use whatsmydns.net or similar tools.

Related Terms: DNS, TTL, Nameserver

Domain

Definition: Human-readable web address (like example.com).

Structure:

subdomain.domain.tld
www.example.com
│   │       │
│   │       └── Top-Level Domain (TLD)
│   └────────── Second-Level Domain (SLD)
└────────────── Subdomain

Types:

• Root/Apex: example.com
• Subdomain: blog.example.com
• WWW: www.example.com

Related Terms: URL, DNS, Registrar, TLD

Downtime

Definition: Period when a service or website is unavailable.

Types:

• Planned: Scheduled maintenance
• Unplanned: Server crashes, attacks, hardware failure

Measurement: Usually expressed as percentage (99.9% uptime = 0.1% downtime)

Uptime Guarantees:

• 99.9% = 8.76 hours/year downtime
• 99.95% = 4.38 hours/year downtime
• 99.99% = 52.56 minutes/year downtime

Related Terms: Uptime, SLA, Availability

E

Email Client

Definition: Software application used to access and manage email.

Types:

Desktop Clients:

• Microsoft Outlook
• Apple Mail
• Mozilla Thunderbird
• Mailbird

Webmail:

• Gmail
• Outlook.com
• Yahoo Mail
• ProtonMail

Mobile Apps:

• iOS Mail
• Gmail app
• Outlook app
• Spark

Protocols Used: IMAP, POP3, SMTP

Related Terms: IMAP, POP3, Webmail

Email Forwarding

Definition: Automatically redirecting emails from one address to another.

Example: sales@company.com → forwards to → john@company.com

Use Cases:

• Consolidate multiple addresses
• Temporary redirection
• Department routing
• Backup delivery

Difference from Alias: Forwarding copies message; alias is same mailbox.

Related Terms: Alias, Redirect, Email Routing

Encryption

Definition: Process of encoding information so only authorized parties can access it.

Types:

Transport Encryption:

• SSL/TLS (in transit)
• Protects during transmission
• HTTPS, SMTPS, IMAPS

End-to-End Encryption:

• Only sender and recipient can read
• Not even server can decrypt
• PGP, S/MIME

At-Rest Encryption:

• Data encrypted on storage
• Protects stored emails
• Requires decryption key

Related Terms: SSL, TLS, Security, Privacy

EPP Code

See Auth Code

F

Firewall

Definition: Security system that monitors and controls incoming and outgoing network traffic.

Types:

• Hardware Firewall: Physical device
• Software Firewall: Application-based
• Cloud Firewall: Distributed protection

Function: Blocks unauthorized access while allowing legitimate traffic.

Rules: Define what traffic is allowed or blocked.

Related Terms: Security, Network, Protection, Ports

FTP (File Transfer Protocol)

Definition: Standard protocol for transferring files between computers over a network.

Variants:

• FTP: Original (port 21, unencrypted)
• FTPS: FTP with SSL/TLS encryption
• SFTP: SSH File Transfer Protocol (port 22, encrypted)

Use Case: Upload website files to server.

Clients: FileZilla, Cyberduck, WinSCP

Modern Alternative: SFTP recommended for security.

Related Terms: Upload, Download, Server Access

G

Gigabyte (GB)

Definition: Unit of digital storage equal to approximately 1 billion bytes.

Exact Value: 1,024 megabytes (MB)

Context:

• Email storage: "10 GB mailbox"
• Bandwidth: "500 GB monthly transfer"
• File size: "2 GB video file"

Related Units:

• 1 GB = 1,024 MB
• 1 TB (terabyte) = 1,024 GB

Related Terms: MB, TB, Storage, Bandwidth

Grace Period

Definition: Time after domain expiration during which you can still renew at normal price.

Duration: Typically 0-45 days (varies by TLD)

During Grace Period:

• ✅ Can renew at standard price
• ⚠️ Services may not work
• ❌ Cannot transfer domain

After Grace Period: Enters redemption (expensive recovery).

Related Terms: Domain Lifecycle, Expiration, Redemption

gTLD (Generic Top-Level Domain)

Definition: Top-level domain not tied to a specific country.

Examples:

• .com - Commercial
• .net - Network
• .org - Organization
• .info - Information
• .biz - Business

New gTLDs:

• .app - Applications
• .tech - Technology
• .store - E-commerce
• .blog - Blogs

Vs. ccTLD: Not country-specific.

Related Terms: TLD, ccTLD, Domain Extension

H

Header (Email)

Definition: Metadata section of an email containing routing and authentication information.

Common Headers:

From: sender@example.com
To: recipient@example.com
Subject: Email subject line
Date: Thu, 24 Oct 2025 10:30:00 -0400
Message-ID: <unique-id@example.com>
Return-Path: bounce@example.com

Technical Headers:

• Received: Mail server route
• DKIM-Signature: Authentication
• SPF: Sender verification
• X-Headers: Custom information

Use Case: Troubleshooting email delivery issues.

Related Terms: SMTP, Email Authentication, Raw Source

Hosting

Definition: Service providing storage space and access for websites or applications.

Types:

Shared Hosting:

• Multiple sites on one server
• Affordable
• Limited resources

VPS Hosting:

• Virtual Private Server
• Dedicated resources
• More control

Dedicated Hosting:

• Entire physical server
• Maximum performance
• Expensive

Cloud Hosting:

• Distributed across multiple servers
• Scalable
• Pay-as-you-go

Related Terms: Server, Domain, Website, Uptime

HTTPS (HTTP Secure)

Definition: Secure version of HTTP using SSL/TLS encryption.

How to Identify: Green padlock icon or "Secure" in browser address bar.

What It Protects:

• Data in transit
• Login credentials
• Payment information
• Personal data

Requirements:

• SSL/TLS certificate
• Proper server configuration

SEO Benefit: Google ranks HTTPS sites higher.

Related Terms: SSL, TLS, Security, Certificate

I

IMAP (Internet Message Access Protocol)

Definition: Email protocol that stores messages on the server and syncs across devices.

Port Numbers:

• Port 143 (unencrypted)
• Port 993 (SSL/TLS encrypted)

Benefits:

• Access from multiple devices
• Messages stay on server
• Folders sync everywhere
• Search server-side

Vs. POP3: IMAP keeps emails on server; POP3 downloads and deletes.

Use Case: Most modern email setups use IMAP.

Related Terms: POP3, SMTP, Email Protocol

Inbox

Definition: Primary folder where incoming emails are delivered.

Organization:

• Main storage for new messages
• Can create subfolders
• Apply filters/rules
• Archive old messages

Zero Inbox: Productivity method of keeping inbox empty.

Related Terms: Mailbox, Folder, Email Management

IP Address (Internet Protocol Address)

Definition: Unique numerical identifier assigned to each device on a network.

Types:

IPv4:

• Format: 192.0.2.1
• 32-bit addresses
• ~4.3 billion possible
• Most common

IPv6:

• Format: 2001:0db8:85a3::8a2e:0370:7334
• 128-bit addresses
• Virtually unlimited
• Future standard

Classes:

• Public IP: Internet-accessible
• Private IP: Local network only
• Static IP: Never changes
• Dynamic IP: Changes periodically

Use Case: Servers need IP addresses to be accessible online.

Related Terms: DNS, A Record, Networking

J

Junk Mail

See Spam

K

Kilobyte (KB)

Definition: Unit of digital storage equal to 1,024 bytes.

Context:

• Small email: "15 KB"
• Text document: "50 KB"
• Small image: "200 KB"

Conversions:

• 1 KB = 1,024 bytes
• 1 MB = 1,024 KB

Related Terms: MB, GB, File Size

L

Latency

Definition: Time delay between request and response in network communication.

Measurement: Milliseconds (ms)

Affects:

• Website load speed
• Email send/receive time
• Application responsiveness

Good Latency: Under 100ms Acceptable: 100-300ms Poor: Over 300ms

Factors:

• Geographic distance
• Network congestion
• Server processing time

Related Terms: Ping, Speed, Performance

Load Balancer

Definition: System that distributes network traffic across multiple servers.

Benefits:

• Prevents server overload
• Increases reliability
• Improves performance
• Enables scaling

How It Works:

1. Traffic arrives at load balancer
2. Balancer checks server health
3. Routes request to available server
4. Distributes load evenly

Use Case: High-traffic websites and applications.

Related Terms: Scaling, Performance, Redundancy

M

Mailbox

Definition: Storage space for emails associated with an email address.

Components:

• Inbox
• Sent items
• Drafts
• Trash/Deleted
• Custom folders

Size: Typically measured in GB (e.g., "10 GB mailbox")

Quota: Maximum storage allowed.

Related Terms: Email Account, Storage, IMAP

Mail Server

Definition: Computer system that sends, receives, and stores email.

Components:

MTA (Mail Transfer Agent):

• Sends/receives between servers
• Examples: Postfix, Sendmail

MDA (Mail Delivery Agent):

• Delivers to mailboxes
• Examples: Dovecot, Courier

Types:

• Outgoing: SMTP server
• Incoming: POP3/IMAP server

Related Terms: SMTP, IMAP, POP3, Email Infrastructure

Megabyte (MB)

Definition: Unit of digital storage equal to 1,024 kilobytes.

Context:

• Email with attachment: "5 MB"
• High-res photo: "3 MB"
• Email limit: "25 MB maximum"

Conversions:

• 1 MB = 1,024 KB
• 1 GB = 1,024 MB

Related Terms: KB, GB, File Size, Storage

MIME (Multipurpose Internet Mail Extensions)

Definition: Standard for formatting non-text email content.

Enables:

• File attachments
• HTML emails
• Images in email
• Multiple character sets

MIME Types:

• text/plain - Plain text
• text/html - HTML content
• image/jpeg - JPEG image
• application/pdf - PDF document

Related Terms: Email, Attachment, Content-Type

MX Record (Mail Exchange)

Definition: DNS record specifying mail servers for receiving email.

Example:

example.com MX 10 mail1.pupam.com
example.com MX 20 mail2.pupam.com

Priority: Lower number = higher priority (10 before 20).

Use Case: Routes incoming email to correct mail server.

Multiple Records: Provides redundancy if primary fails.

Related Terms: DNS, Email, Mail Server

N

Nameserver

Definition: Server that translates domain names into IP addresses.

Example:

ns1.pupam.com
ns2.pupam.com
ns3.pupam.com
ns4.pupam.com

Function: Stores DNS records for domains.

Hierarchy:

• Root nameservers (13 globally)
• TLD nameservers (.com, .net, etc.)
• Authoritative nameservers (your domain)

Multiple Servers: Redundancy and load distribution.

Related Terms: DNS, A Record, Domain

NS Record (Nameserver Record)

Definition: DNS record delegating a domain to specific nameservers.

Example:

example.com NS ns1.pupam.com
example.com NS ns2.pupam.com

Use Case: Points domain to DNS servers that manage its records.

Critical: Incorrect NS records break everything!

Related Terms: Nameserver, DNS, Domain Delegation

O

Open Rate

Definition: Percentage of email recipients who open an email.

Calculation: (Emails opened / Emails delivered) × 100

Tracking: Usually via invisible tracking pixel.

Average Rates:

• Industry average: 15-25%
• Good: 25-35%
• Excellent: 35%+

Factors:

• Subject line quality
• Sender reputation
• Send time
• List quality

Related Terms: Email Marketing, CTR, Engagement

Outbound Email

Definition: Emails sent from your mail server to recipients.

Includes:

• Business correspondence
• Marketing emails
• Automated notifications
• Newsletters

Limits: Some servers have daily sending limits.

Monitoring: Track for reputation management.

Related Terms: SMTP, Sending, Email Campaign

P

Phishing

Definition: Fraudulent attempt to obtain sensitive information by impersonating legitimate entities.

Common Tactics:

• Fake login pages
• Urgent action requests
• Suspicious links
• Requests for personal info

Red Flags:

• ⚠️ Unknown sender
• ⚠️ Poor grammar/spelling
• ⚠️ Urgent threats
• ⚠️ Suspicious links
• ⚠️ Requests for passwords

Protection:

• Verify sender
• Don't click suspicious links
• Enable 2FA
• Use anti-phishing tools

Related Terms: Spam, Security, Social Engineering

POP3 (Post Office Protocol 3)

Definition: Email protocol that downloads messages from server to device.

Port Numbers:

• Port 110 (unencrypted)
• Port 995 (SSL/TLS encrypted)

How It Works:

1. Connects to mail server
2. Downloads all new messages
3. Deletes from server (usually)
4. Stores locally on device

Vs. IMAP: POP3 downloads and removes; IMAP keeps on server.

Use Case: Single device access, offline reading.

Related Terms: IMAP, SMTP, Email Protocol

Port

Definition: Virtual numbered channel for network communications.

Common Email Ports:

• 25: SMTP (standard)
• 587: SMTP (submission, encrypted)
• 465: SMTPS (SSL/TLS)
• 110: POP3 (unencrypted)
• 995: POP3S (SSL/TLS)
• 143: IMAP (unencrypted)
• 993: IMAPS (SSL/TLS)

Common Web Ports:

• 80: HTTP
• 443: HTTPS
• 21: FTP
• 22: SSH/SFTP

Blocked Ports: Some ISPs block port 25 to prevent spam.

Related Terms: Protocol, SMTP, Network

Q

Queue

Definition: System that holds emails waiting to be processed or delivered.

Types:

Outgoing Queue:

• Emails waiting to send
• May be delayed by rate limits
• Processing in order

Incoming Queue:

• Emails awaiting delivery to mailbox
• Spam filtering in progress
• Virus scanning

Stuck in Queue:

• Server issues
• Recipient problems
• Network delays
• Configuration errors

Related Terms: Mail Server, Delivery, SMTP

Quota

Definition: Maximum amount of storage space allocated to a mailbox or account.

Example: "Your mailbox has a 10 GB quota"

What Counts:

• Stored emails
• Attachments
• Trash folder
• Sent items

When Full:

• Cannot receive new emails
• Incoming mail bounces
• Must delete or archive

Management: Regular cleanup, archiving old emails.

Related Terms: Storage, Mailbox, Disk Space

R

Ransomware

Definition: Malicious software that encrypts files and demands payment for decryption.

How It Spreads:

• Email attachments
• Malicious links
• Compromised websites
• Software vulnerabilities

Protection:

• Regular backups
• Anti-malware software
• Email filtering
• User education
• Keep software updated

Response:

• Disconnect from network
• Don't pay ransom
• Report to authorities
• Restore from backup

Related Terms: Malware, Security, Backup

Redirect

See Email Forwarding

Registrar

Definition: Company authorized to sell and manage domain name registrations.

Popular Registrars:

• GoDaddy
• Namecheap
• Google Domains
• Hover
• PUPAM

Services Provided:

• Domain registration
• Domain transfer
• DNS management
• WHOIS privacy
• Auto-renewal

ICANN Accreditation: Must be accredited to sell domains.

Related Terms: Domain, Registry, DNS, Transfer

Registry

Definition: Organization that manages all domain names within a specific TLD.

Examples:

• Verisign: .com, .net
• PIR: .org
• Google Registry: .google, .app
• ICANN: Oversees all

Role:

• Maintains TLD database
• Sets policies
• Technical operations
• Works with registrars

Note: You register through registrar, not registry directly.

Related Terms: Registrar, TLD, Domain, ICANN

Relay

Definition: Process of forwarding email through multiple servers to reach destination.

Open Relay: Server that accepts and forwards mail from anyone (security risk!).

Authorized Relay: Only forwards mail from authenticated users.

Relay Host: Mail server designated to send outgoing mail.

Related Terms: SMTP, Mail Server, Email Routing

Reputation (Sender)

Definition: Trustworthiness score assigned to email sender's IP address or domain.

Affects:

• Email deliverability
• Spam folder placement
• Inbox arrival rate
• ISP filtering

Factors:

• Spam complaints
• Bounce rates
• Sending volume
• Authentication (SPF, DKIM, DMARC)
• Blacklist status
• Engagement rates

Monitoring: Use tools like Sender Score, Google Postmaster.

Related Terms: Deliverability, Blacklist, SPF, DKIM

Reverse DNS (rDNS)

Definition: DNS lookup that resolves IP address to domain name (opposite of normal DNS).

Example:

• Normal: example.com → 192.0.2.1
• Reverse: 192.0.2.1 → mail.example.com

Use Case: Email servers check reverse DNS to verify sender legitimacy.

PTR Record: DNS record type used for reverse DNS.

Important: Reverse DNS should match forward DNS for email servers.

Related Terms: DNS, PTR Record, Email Authentication

S

SaaS (Software as a Service)

Definition: Software delivery model where applications are hosted and accessed via internet.

Examples:

• Gmail (email)
• Microsoft 365 (productivity)
• Salesforce (CRM)
• Slack (communication)

Benefits:

• No installation needed
• Accessible anywhere
• Automatic updates
• Subscription pricing

Vs. Traditional: No local installation or maintenance.

Related Terms: Cloud, Web-Based, Subscription

Shared Hosting

Definition: Hosting where multiple websites share resources on a single server.

Pros:

• ✅ Affordable
• ✅ Easy to use
• ✅ Maintained by provider
• ✅ Good for small sites

Cons:

• ❌ Limited resources
• ❌ Shared IP address
• ❌ "Noisy neighbor" effect
• ❌ Less control

Good For: Personal blogs, small business sites, low-traffic websites.

Related Terms: Hosting, VPS, Dedicated Server

SLA (Service Level Agreement)

Definition: Contract specifying guaranteed service levels and compensation for failures.

Common Guarantees:

• Uptime: 99.9%, 99.95%, 99.99%
• Response time: Within X hours
• Resolution time: Within Y days
• Support availability: 24/7, business hours

Compensation: Credits or refunds for SLA violations.

Example: "99.9% uptime guarantee with account credit if exceeded"

Related Terms: Uptime, Downtime, Guarantee

SMTP (Simple Mail Transfer Protocol)

Definition: Protocol for sending emails between servers and from clients to servers.

Ports:

• 25: Standard SMTP
• 587: Submission (recommended)
• 465: SMTPS (SSL/TLS)

How It Works:

1. Client connects to SMTP server
2. Authenticates (username/password)
3. Sends email content
4. Server relays to recipient's server
5. Recipient's server delivers to mailbox

Settings Needed:

• SMTP server address
• Port number
• Authentication credentials
• Encryption method

Related Terms: IMAP, POP3, Email Protocol, Port

Spam

Definition: Unsolicited bulk email sent to many recipients.

Types:

• Commercial advertising
• Phishing attempts
• Malware distribution
• Scams and fraud

Filtering Methods:

• Content analysis
• Sender reputation
• Blacklists
• Bayesian filtering
• Machine learning

Reporting: Mark as spam helps train filters.

Protection: Use spam filters, don't share email publicly.

Related Terms: Junk Mail, Phishing, Filter, Blacklist

SPF (Sender Policy Framework)

Definition: Email authentication method specifying which mail servers can send on behalf of your domain.

DNS Record Example:

example.com TXT "v=spf1 include:_spf.pupam.com ~all"

How It Works:

1. Receiving server checks SPF record
2. Verifies sender's IP is authorized
3. Passes or fails based on match

Results:

• Pass: IP authorized
• Fail: IP not authorized
• Softfail: Probably not authorized (~)
• Neutral: No policy

Benefits: Prevents email spoofing, improves deliverability.

Related Terms: DKIM, DMARC, Email Authentication

SRV Record (Service Record)

Definition: DNS record specifying location of specific services.

Format:

_service._protocol.domain TTL class SRV priority weight port target

Example:

_sip._tcp.example.com 3600 IN SRV 10 5 5060 sipserver.example.com

Use Cases:

• VoIP/SIP services
• XMPP/Jabber
• LDAP
• Gaming servers

Related Terms: DNS, Service Discovery

SSL/TLS (Secure Sockets Layer / Transport Layer Security)

Definition: Cryptographic protocols that provide secure communication over networks.

What They Protect:

• Login credentials
• Personal information
• Payment data
• Email content

Visual Indicators:

• 🔒 Padlock icon
• HTTPS in URL
• "Secure" label

Certificate Types:

• Domain Validation (DV): Basic
• Organization Validation (OV): Medium
• Extended Validation (EV): Highest

Providers:

• Let's Encrypt (free)
• DigiCert
• Comodo
• GlobalSign

Related Terms: HTTPS, Certificate, Encryption, Security

Subdomain

Definition: Subdivision of a main domain, appearing before the domain name.

Structure: subdomain.domain.tld

Examples:

• blog.example.com
• shop.example.com
• mail.example.com
• app.example.com

Use Cases:

• Separate sections of website
• Different services (mail, ftp)
• Development environments
• Regional variations

DNS: Requires separate A or CNAME record.

Related Terms: Domain, DNS, A Record

T

TCP/IP (Transmission Control Protocol / Internet Protocol)

Definition: Fundamental communication protocols that enable internet connectivity.

TCP: Ensures reliable data transmission. IP: Routes data packets to correct destination.

How It Works:

1. Data broken into packets
2. Each packet routed independently
3. TCP ensures all arrive correctly
4. Data reassembled at destination

Use Case: Foundation of all internet communication.

Related Terms: Network, Protocol, Internet

Terabyte (TB)

Definition: Unit of digital storage equal to 1,024 gigabytes.

Context:

• Large email archive: "2 TB storage"
• Server storage: "500 TB capacity"
• Backup: "10 TB monthly backup"

Conversions:

• 1 TB = 1,024 GB
• 1 PB (petabyte) = 1,024 TB

Related Terms: GB, Storage, Capacity

TLD (Top-Level Domain)

Definition: Highest level in the domain name hierarchy (everything after the final dot).

Categories:

gTLD (Generic):

• .com, .net, .org, .info

ccTLD (Country Code):

• .us, .uk, .ca, .de

New gTLD:

• .app, .tech, .blog, .store

sTLD (Sponsored):

• .gov, .edu, .mil

Related Terms: Domain, gTLD, ccTLD, Extension

TTL (Time to Live)

Definition: Duration (in seconds) that DNS records are cached.

Examples:

• 300: 5 minutes (low, fast updates)
• 3600: 1 hour (standard)
• 86400: 24 hours (high, stable)

Low TTL:

• ✅ Quick updates
• ❌ More DNS queries

High TTL:

• ✅ Fewer queries
• ✅ Better performance
• ❌ Slower changes

Use Case: Lower TTL before making DNS changes.

Related Terms: DNS, Caching, Propagation

TXT Record

Definition: DNS record storing text information for various purposes.

Common Uses:

SPF (Email Authentication):

v=spf1 include:_spf.pupam.com ~all

DKIM (Signature):

v=DKIM1; k=rsa; p=MIGfMA0GCSq...

Domain Verification:

google-site-verification=abc123xyz

DMARC:

v=DMARC1; p=quarantine; rua=mailto:dmarc@example.com

Limit: 255 characters per string (can use multiple).

Related Terms: DNS, SPF, DKIM, Verification

U

Uptime

Definition: Percentage of time a service is operational and accessible.

Calculation: (Total time - Downtime) / Total time × 100

Common Guarantees:

Monitoring: Use uptime monitoring services.

Related Terms: Downtime, SLA, Availability, Reliability

URL (Uniform Resource Locator)

Definition: Complete web address specifying location of a resource.

Structure:

protocol://subdomain.domain.tld/path/page.html?query=value#anchor
https://www.example.com/blog/post.html?id=123#section2
│      │ │   │       │   │    │        │       │
│      │ │   │       │   │    │        │       └─ Anchor/Fragment
│      │ │   │       │   │    │        └───────── Query string
│      │ │   │       │   │    └────────────────── Path/Page
│      │ │   │       │   └─────────────────────── TLD
│      │ │   │       └─────────────────────────── Domain
│      │ │   └─────────────────────────────────── Subdomain
│      │ └─────────────────────────────────────── Domain separator
│      └───────────────────────────────────────── Protocol

Related Terms: Domain, URI, Link, Hyperlink

V

Virus

Definition: Malicious software that replicates by inserting copies into other programs or files.

Distribution Methods:

• Email attachments
• Downloaded files
• Infected websites
• USB drives

Types:

• File virus: Infects executable files
• Macro virus: Infects documents
• Boot sector virus: Infects startup
• Polymorphic virus: Changes to avoid detection

Protection:

• Antivirus software
• Email filtering
• Regular scans
• Software updates
• User awareness

Related Terms: Malware, Antivirus, Security, Threat

VPS (Virtual Private Server)

Definition: Virtualized server providing dedicated resources within a shared physical server.

How It Works:

• Physical server divided virtually
• Each VPS isolated from others
• Dedicated CPU, RAM, storage
• Full root access

Vs. Shared Hosting:

• ✅ Dedicated resources
• ✅ Better performance
• ✅ More control
• ✅ Custom software
• ❌ More expensive

Vs. Dedicated:

• ✅ More affordable
• ✅ Scalable
• ❌ Shared physical hardware

Good For: Growing websites, applications, development environments.

Related Terms: Hosting, Cloud, Server, Resources

W

Webmail

Definition: Email access through a web browser instead of dedicated email client.

Popular Services:

• Gmail
• Outlook.com
• Yahoo Mail
• ProtonMail

Benefits:

• ✅ Access from any device
• ✅ No software installation
• ✅ Automatic updates
• ✅ Built-in spam filtering

Limitations:

• ❌ Requires internet
• ❌ Less offline functionality
• ❌ Limited customization

Related Terms: Email Client, Browser, Cloud Email

WHOIS

Definition: Protocol and database for querying domain registration information.

Information Provided:

• Registrant name/organization
• Registration date
• Expiration date
• Nameservers
• Registrar
• Contact information
• Domain status

Privacy Protection: Hides personal information (available for extra fee).

How to Check:

whois example.com

Or use online tools like whois.pupam.com

Uses:

• Verify ownership
• Check availability
• Contact domain owner
• Domain research

Related Terms: Domain, Registration, Privacy

X

X-Headers

Definition: Custom email headers starting with "X-" used for non-standard information.

Examples:

X-Mailer: Microsoft Outlook
X-Spam-Score: 3.2
X-Priority: 1 (Highest)
X-Campaign-ID: newsletter-2025-10
X-Custom-Field: special-value

Uses:

• Spam scoring
• Email tracking
• Custom data
• Debugging
• Campaign identification

Note: Modern headers may not use "X-" prefix anymore.

Related Terms: Email Header, SMTP, Metadata

Y

Yottabyte (YB)

Definition: Enormous unit of digital storage equal to 1,024 zettabytes.

Scale: 1 YB = 1,024 ZB = 1,048,576 EB = 1,073,741,824 TB

Context: Theoretical scale, rarely used in practice. All data on the internet estimated at ~100 ZB (less than 1 YB).

Related Terms: TB, PB, EB, ZB, Storage

Z

Zero-Day

Definition: Security vulnerability unknown to software vendor or without available patch.

Threat Level: HIGH - Attackers can exploit before fix available.

Timeline:

1. Vulnerability exists (unknown)
2. Discovered by attacker (zero-day)
3. Exploited
4. Discovered by vendor
5. Patch developed
6. Patch released

Protection:

• Keep software updated
• Use security tools
• Monitor for unusual activity
• Employ defense-in-depth

Related Terms: Security, Vulnerability, Exploit, Patch

Zettabyte (ZB)

Definition: Unit of digital storage equal to 1,024 exabytes.

Scale: 1 ZB = 1,024 EB = 1,048,576 PB = 1,073,741,824 TB

Context:

• Global IP traffic: ~4.8 ZB per year (2022)
• All data on internet: ~100 ZB

Related Terms: TB, PB, EB, YB, Storage

Quick Reference: Common Acronyms

Email & Authentication:

• SPF - Sender Policy Framework
• DKIM - DomainKeys Identified Mail
• DMARC - Domain-based Message Authentication, Reporting & Conformance
• SMTP - Simple Mail Transfer Protocol
• IMAP - Internet Message Access Protocol
• POP3 - Post Office Protocol 3
• MIME - Multipurpose Internet Mail Extensions

DNS & Domains:

• DNS - Domain Name System
• TLD - Top-Level Domain
• gTLD - Generic Top-Level Domain
• ccTLD - Country Code Top-Level Domain
• TTL - Time to Live
• CAA - Certification Authority Authorization

Security:

• SSL - Secure Sockets Layer
• TLS - Transport Layer Security
• 2FA - Two-Factor Authentication
• DDoS - Distributed Denial of Service

Technical:

• API - Application Programming Interface
• CPU - Central Processing Unit
• RAM - Random Access Memory
• VPS - Virtual Private Server
• SaaS - Software as a Service
• FTP - File Transfer Protocol
• HTTP - Hypertext Transfer Protocol
• HTTPS - HTTP Secure
• IP - Internet Protocol
• TCP - Transmission Control Protocol
• URL - Uniform Resource Locator

Storage:

• KB - Kilobyte (1,024 bytes)
• MB - Megabyte (1,024 KB)
• GB - Gigabyte (1,024 MB)
• TB - Terabyte (1,024 GB)
• PB - Petabyte (1,024 TB)

Need More Help?

Can't find a term? Contact our support team:

• Email: support@pupam.com
• Live Chat: Available 24/7
• Phone: +1 (555) 123-SUPPORT

Suggest a term: If there's a technical term you'd like us to add, email dictionary@pupam.com

Last Updated: October 24, 2025
Version: 1.0
Maintained by: Technical Documentation Team