Glossary
Email: terms A–Z
Every business email term explained in plain English — SMTP, IMAP, SPF, DKIM, DMARC, deliverability, and more.
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Business email has layers of technical vocabulary — especially around deliverability, security, and configuration. This page is your reference for every term you'll encounter.
Quick summary
This page covers 55+ email terms from A to Z. For step-by-step email guides, visit the Email section. Use Ctrl+F / Cmd+F to jump to any term.
A–C
| Term | Plain-English definition |
|---|---|
| Alias | An additional email address that delivers to an existing inbox. E.g. hello@yourcompany.com forwarding to sarah@yourcompany.com. See Email aliases & forwarding explained. |
| Archive | A searchable store of old email messages. Some organizations are legally required to archive emails for a period of time. |
| Auto-reply | An automatic message sent in response to incoming email — e.g. "Thanks for your email, I'll respond within 24 hours." |
| Blacklist | A list of email servers or domains known to send spam. If your domain gets blacklisted, your emails may be blocked or sent to junk. |
| Bounce | When an email cannot be delivered and is returned to the sender. A hard bounce means the address doesn't exist; a soft bounce is a temporary issue (e.g. full inbox). |
| Catch-all address | An email address that receives messages sent to any nonexistent address at your domain — so nothing gets lost. |
| CC | Carbon copy. Sends a copy of an email to additional recipients who can see each other's names. |
| Client | Short for email client — the app or program you use to read and send email (Outlook, Apple Mail, Gmail in a browser). |
D–I
| Term | Plain-English definition |
|---|---|
| Deliverability | How reliably your emails reach recipients' inboxes (rather than spam folders). Affected by SPF, DKIM, DMARC, and sending reputation. See Why your emails land in spam (deliverability). |
| Distribution list | A group email address that delivers to a list of recipients. Useful for team-wide announcements. See Group & distribution lists explained. |
| DKIM | DomainKeys Identified Mail. A digital signature added to outgoing emails proving they genuinely came from your domain. See SPF, DKIM & DMARC for email senders. |
| DMARC | Domain-based Message Authentication, Reporting & Conformance. A policy that tells receiving servers what to do with emails that fail SPF or DKIM checks. |
| Domain | The part of an email address after the @. In sarah@yourcompany.com, the domain is yourcompany.com. |
| Encryption | Scrambling email content so only the intended recipient can read it. TLS encryption protects emails in transit. |
| Forwarding | Automatically sending copies of received emails to another address. |
| Google Workspace | Google's paid suite of business tools that includes Gmail with a custom domain. See What is Google Workspace?. |
| Header | Hidden technical metadata in an email that shows its routing path, authentication results, and timestamps. Useful for diagnosing delivery problems. |
| IMAP | Internet Message Access Protocol. The protocol that lets email clients sync messages from a mail server — so your emails stay on the server and appear across all your devices. |
| Inbox | The folder where received emails land. |
J–O
| Term | Plain-English definition |
|---|---|
| Junk folder | See Spam folder. |
| Mail server | A computer that sends, receives, and stores email on behalf of your domain. |
| Marketing email | Promotional email sent to lists — newsletters, campaigns, offers. Should go through dedicated platforms like Mailchimp or Klaviyo. See Transactional vs marketing email. |
| Microsoft 365 | Microsoft's paid suite that includes Outlook with a custom domain. See What is Microsoft 365?. |
| MX record | Mail Exchange DNS record. Tells the internet which mail server handles email for your domain. See DNS records explained. |
| Out-of-office reply | An automatic message sent when you're away, telling senders when you'll be back. See Out-of-office & auto-replies. |
P–R
| Term | Plain-English definition |
|---|---|
| Phishing | A fraudulent email that pretends to be from a trusted company or person, attempting to steal login details or money. See How to recognize a phishing email. |
| POP3 | Post Office Protocol 3. An older protocol that downloads emails to your device and removes them from the server. Less common now — IMAP is preferred. |
| Reply-to address | A different address that replies go to, even if the email was sent from another address. Common in marketing campaigns. |
| Reputation | The trustworthiness score of your sending domain and mail server in the eyes of email providers. High reputation = better deliverability. |
S–Z
| Term | Plain-English definition |
|---|---|
| Sender score | A numerical rating of your email sending reputation. Affects whether emails reach inboxes. |
| Shared mailbox | An inbox multiple people can access and send from — e.g. support@yourcompany.com. See Shared mailboxes (like support@) explained. |
| Signature | Automatic text appended to the bottom of every email — name, title, phone, website. See Creating a professional email signature. |
| SMTP | Simple Mail Transfer Protocol. The standard protocol for sending email between servers (and from apps to your mail server). See What is SMTP (and why your site needs it)?. |
| Spam | Unsolicited bulk email. Also the folder where suspected junk email lands. |
| SPF | Sender Policy Framework. A DNS record that lists which servers are authorized to send email from your domain. See SPF records, explained. |
| TLS | Transport Layer Security. Encryption that protects emails while they're being transmitted between servers. |
| Transactional email | Automated email triggered by a user action — order confirmation, password reset, account notification. Should use dedicated SMTP services like SendGrid or Postmark. |
| Unsubscribe | The process a recipient uses to stop receiving marketing email. Including an unsubscribe link in marketing email is legally required in most countries. |
| Webmail | Accessing your email through a web browser instead of an installed app. See Accessing email on the web. |
| Whitelist | A list of senders whose emails should always be delivered (never filtered as spam). Also called a safe senders list. |
Common questions
Related guides
- Business email, explained
- Why your emails land in spam (deliverability)
- SPF, DKIM & DMARC for email senders
- What is SMTP?
- Email terms, explained simply
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