Building notes, projects, and occasional rants

SMTP is alive and kicking

The new RFCs for SMTP (RFC 5321) and Internet Message Format (RFC 5322) where released yesterday.

You can find a list of changes in the MailChannels blog.

The most user-visible change is that port 587 is finally recommended for end-users, reserving 25 for MTA-to-MTA traffic. Also, use of SMTP for end-user clients is discouraged, pointing them to the Message Submission for Mail (RFC 4409) protocol.

For server operators, a lot of blessings to current behaviors:

  • you can now legally reject an email after the DATA is complete: yes, most anti-virus/anti-spam appliances already did that, but it was not legal;
  • timeouts are legal too.

It seems a pretty decent upgrade.