Email technical
Protocols, encodings and technical terms.
- AMP for Email
A format that lets an email contain interactive elements such as forms and carousels.
- API
An application programming interface: a defined way for one program to ask another to do something.
- APOP
Authenticated Post Office Protocol: an optional POP3 login method that uses a challenge-response instead of sending the password directly.
- Attachment
A file sent along with an email message.
- Base64
A way of writing binary data as plain text characters.
- Bot detection
Techniques that tell automated visitors from people, used on forms and when measuring email engagement.
- DDoS
A distributed denial-of-service attack: many machines flood a service with traffic until it cannot respond.
- DNS TXT record
A DNS record that holds free-form text.
- Email address fields
The header fields of a message that hold addresses: From, To, Cc, Bcc, Reply-To and Return-Path.
- Email case sensitivity
Whether upper and lower case matter in an address.
- Email domain
The part of an address after the @, which decides where mail for that address is delivered.
- Email encryption
Protecting message content from being read by anyone but the intended parties.
- Email forwarding
Passing a received message on to another address, by hand or by an automatic rule.
- Email gateway
A server or service at the edge of an organisation’s mail system that filters inbound and outbound messages.
- Email header
The lines of metadata at the top of a message: From, To, Date, Subject, Message-ID and the Received lines each server adds.
- Email hosting
A service that provides mailboxes for your domain.
- Email infrastructure
Everything that sends your mail: domains, sending IPs, mailboxes, DNS records and the platform.
- Email logs
Records of what happened to each message: accepted, deferred, delivered or bounced, with the reason.
- Email migration
Moving mailboxes or lists from one provider or platform to another.
- Email one-time passcode
A short code sent by email to prove a person controls an address or to log them in.
- Email parser
Software that reads incoming messages and extracts structured data, such as order details or lead fields.
- Email protocol
A standard way for systems to exchange mail: SMTP to send, IMAP and POP3 to read.
- Email queue
The waiting line of outbound messages a server or platform processes.
- Email rate limiting
Limits on how many messages or requests are allowed in a period.
- Email relay
A server that accepts mail and passes it on to another server.
- Email rendering
How an email client draws the HTML of a message.
- Email routing
How a message finds its way from sender to mailbox.
- Email security
Protecting email accounts and messages from abuse.
- Email server
Software that sends, receives and stores email for a domain.
- Email spoofing
Forging the sender of a message so it appears to come from someone else.
- Email standards
The published specifications that email systems follow.
- Email validation
Checking that an address is correctly formed.
- Email worm
Malware that spreads by emailing copies of itself to the contacts it finds on an infected machine.
- Gigabyte (GB)
A unit of storage, about a billion bytes, used for mailbox size and attachment limits.
- Google Workspace
Google’s business suite, which hosts company email on a custom domain among other services.
- Greylisting
An anti-spam method where a server temporarily rejects the first message from an unknown sender and accepts a later retry.
- Honeypot
A trap used against abuse: either a hidden form field that bots fill in, or an address that exists only to catch spam senders.
- Host name
The name of a server, such as mail.example.test.
- HTML email
A message formatted with HTML rather than plain text.
- Image blocking
A mail client setting that does not load images in a message until the reader allows it.
- IMAP
Internet Message Access Protocol: how a mail client reads mail that stays stored on the server.
- IMAP IDLE
An IMAP extension that keeps a connection open so the server can tell the client at once when new mail arrives.
- Inbound email
Email that arrives at your system, as opposed to email you send.
- IP address
The number that identifies a machine on the internet, which is how mail servers are known to each other.
- LDAP
Lightweight Directory Access Protocol: a standard way to look up entries in a directory of people and resources.
- List-Unsubscribe header
A message header that lets mail apps show an unsubscribe button next to your message.
- Mail bomb
A flood of messages aimed at one inbox to bury it or knock it out.
- Mail loop
Messages passing back and forth between systems without end, usually from two auto-replies answering each other or a bad forwarding rule.
- MAILER-DAEMON
The automatic sender name on bounce messages that a mail server generates.
- mailto link
A link that opens a new email to a given address, written as mailto:name@example.test.
- MIME
Multipurpose Internet Mail Extensions: the standard that lets email carry attachments, non-English text and several versions of the same message.
- MTA
Mail Transfer Agent: server software that moves messages between mail servers.
- MUA
Mail User Agent: the program a person uses to read and write email, such as a mail app.
- MX record
A DNS record that names the mail servers for a domain and their priority.
- Phishing email
A fraudulent message designed to trick a person into giving away credentials or money.
- Plain text email
A message with no formatting, images or links to styled elements.
- POP3
Post Office Protocol version 3: a way for a mail client to download messages from a server.
- Postmaster
The standard mailbox, postmaster@yourdomain, that a mail domain should keep for reporting delivery problems; also the name of providers’ sender dashboards.
- PST file
The file format Outlook uses to store mail, contacts and calendar items offline.
- Ransomware
Malware that encrypts a victim’s files and demands payment to unlock them.
- Reply-To
A header that tells the recipient’s mail app where replies should go.
- Return-Path
The address where bounces and delivery notices are sent, also called the envelope sender.
- Rich text
Text with formatting, such as bold, italics, lists and links.
- S/MIME
Secure/Multipurpose Internet Mail Extensions: a way to sign and encrypt email using certificates.
- SMTP
Simple Mail Transfer Protocol: the standard for sending email between servers and from clients to servers.
- SSL
Secure Sockets Layer, the old protocol for encrypting connections; today the name is often used for its successor, TLS.
- Threadjacking
Inserting a message into an existing email conversation so it looks like a legitimate reply.
- Tracking pixel
A tiny image in an email that records when a message is opened.
- Typosquatting
Registering domains that look like real ones, such as a common misspelling, to catch mistyped mail or trick people.
- Unicode
The standard that gives every character, in every language, a number so text can be shared between systems.
- Webhooks
Messages that a service sends to a web address you provide when something happens, instead of you asking repeatedly.