Sieve filtering

Sieve is a mail filtering language that can be used to place emails in folders, reject or discard emails, and forward an email to another user. DBMail uses libSieve that implements rfc 3028.

Although rfc 5228 has obsoleted 3028, it is largely the same and so libSieve remains the library used to implement Sieve.

dbmail-sieved implements a subset of RFC 5804 Remotely Managing Sieve Scripts.

dbmail-deliver and dbmail-lmtpd implement rfc 3028 when sieve is set in dbmail.conf.