Guidelines for accepting email messages as input to application

Question

A number of applications have the handy feature of allowing users to respond to notification emails from the application. The responses are slurped back into the application.

Answer 1

Bose has a pretty great system where they embed a Queue and Ticket ID into the email itself.

My company has the traditional Case # on the subject line, but when CREATING a case, require a specific character string "New Case" "Tech Support Issue" on the subject line to get through the spam filters.

If the email doesn't match the create or update semantics, the autoresponder sends an email back to the recipient demonstrating how to properly send an email, or directs them to our forums or web support site.

It helps eliminate the spam issue, and yet is still accessible to a wide technical audience that is still heavily email dependent.