This is a question / rfc-initiator I posted on my old blog:

Does anybody know if there is an SMTP header that allows me to specify that a message is a notification-message, and one to set the expiration date / TTL?

A lot of emails I receive are notification messages (new message on facebook, build failed, etc). Some of these have an expiration-time (password reset-token should be redeemed in 4 hours).

It would be nice if the mailclient (gmail) could identify those messages, and handle them in a different way. For example: 

• Notification mails should be forwarded to my IM
• Notification mails marked as urgent should be texted/sms’ed
• E-mail with a TTL, should automatically be deleted/archived

What do you think?