Honeypot mode

[MTRNord]

This is more a "cool to have" feature to add along the way and should be a compiletime flag.

Basically I receive lots of spam on my test instance. I was wondering if I can safely accept this.

The differences needed would be:

• It should pretend to accept stuff and behave like an open relay
• It should fully not compile the sending parts of the server to make sure this doesnt actually send emails ever.
• It should send things to rspamd
• It should log the content and requests to a file format on disk
• It should generate a list of shasums to check if we got it before.
  • The sum must be only over the body
  • If it is seen multiple times we record the target address among the previous attempt
• We should record the rspamd result
• We should auto commit new files to git
• We should have a way to send undetected things to rspamd to make sure they have learned this.