Implicit keep works.
Explicit keep works.
Fileinto works.
Discard works.
Redirect appears to work (not yet tested with a full mail stack).
Reject merely discards, but it should also return an appropriate
rejection exit code (smtp) or 5xx code (lmtp). I'm working on vacation
and subaddress this
Progress!
Reject returns a failure code.
Subaddress works with the forthcoming libSieve 2.1.9.
Vacation works at the Sieve level, but isn't coded up in DBMail. I'm not
happy with the amount of code duplication in pipe.c, and would like to
have send_reply, send_notification and send_vacation
