Adding a junk button to MUAs
Most web mail systems have a button a user can push to mark a message as junk, and report it back to their mail host. How would one add a similar button to a regular MUA? For the purposes of this discussion, the goal is to report the message back to the user's own mail system. They might further report it to the place the message came from, but that's a separate discussion.
Two somewhat separate issues are:
- How a message that is reported in the MUA is sent back to the mail system
- How a MUA knows when reporting is available
Sending back reported messages
The two general approaches seem to be to send it back via the path it arrived, typically POP or IMAP, or to use a separate path, such as SMTP or SUBMIT.