Mail Protocols

An enumeration and description of the three major email protocols.

Sending and receiving emails is surprisingly complicated. Luckily, I've covered the basics of SMTP, IMAP and POP3 over here.

SMTP

The one that sends emails.

IMAP

The first one that receives emails. Stores emails on the mail server, allowing you to read emails from anywhere with the right login credentials.

POP3

The other one that receives emails. Forces the recipient to download the email from the mail server before reading it To save space, I suppose.

DomainKeys-Identified-Mail

The first one that validates emails. Checks only for a valid, non-spoofed domain from the sender.

Sender-Policy-Framework

The other one that validates emails. Not only checks for a non-spoofed domain from the sender, but also double-checks the IP of the sender's domain against the one registered in the DNS records.

Domain-based Message Authentication, Reporting, and Conformation

The last one that validates emails. Combines DKIM and SPF, but then allows you to make a 'spam' mailbox so that flagged messages aren't just blocked & tossed.

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