Electronic mail (email or e-mail) is a method of exchanging human-readable messages between electronic devices. Its usage today is covered by several protocols that handle different aspects of the mail exchange - although there is some overlap between them.
Email Agent Infrastructure
- MUA: Mail User Agent
- MAA: Message Accessing Agent
- MSA: Message Submission Agent
- MTA: Mail Transfer Agent
- MDA: Mail Delivery Agent
- MRA: Mail Retrieval Agent
Email Protocols
- IMAP: Internet Mail Access Protocol
- POP3: Post Office Protocol 3
- SMTP: Simple Mail Transfer Protocol
IMAP and POP3 are protocols for communication between a mail client and a mail server. This includes:
- Retrieve mail
- Send mail
- Organize mails
The Email server will use SMTP for communication between mail servers.
- Sending mail
- Rejecting mail
- Exchange information about e.g. a non-existent recipient for a mail
POP3 vs IMAP
POP3
- Only allows downloading inbox
- Mail gets deleted when retrieving (delete mode), or remains (keep mode)
- No synchronisation between folders
- One device at a time
- No organization of the mails on the mail server
- Port 110, Port 995 (SSL)
IMAP
- Synchronisation between folders, e.g. sent/drafts/deleted
- Multiple devices can access messages
- Direct organization of the mails by the user on the server
- Port 143, Port 993 (SSL)
Email etiquette
- Prefer plaintext over HTML
- Use "bottom posting" over "top posting": Don't put your message above the quoted version of the mail you are replying to. Instead, trim the quote to the relevant parts you are replying to and put that quote underneath.
- Wrap your text at 72 columns. Optionally also wrap the quoted parts.