Email standards

Email structure

These RFCs define the way emails themselves are structured.

Email protocols

These RFCs define how emails are transported between computers, both for sending (SMTP) and receiving (IMAP/POP).

Email security

These RFCs define some security standards for email protocols and formats.

We also support ARC, a way to sign a message after it has passed through intermediate mail servers (for instance, through forwarding). ARC is currently a draft standard with the IETF, and resolves some of the drawbacks of DKIM.

Service discovery

Email software that wants to access a user's email account has to know the server(s) to connect to. This used to be manually configured, but nowadays is often done using the user's email address through a service discovery process.

Note that some software vendors seem to maintain their own database of email domain → server name definitions to support auto-configuration in their email clients. These seem to be custom databases maintained by each software vendor separately.