It adds the ability to manually invoke Sieve filtering in IMAP.

When this is enabled for a mailbox rule, the specified Sieve script is executed for the message in the source mailbox during a "COPY" event.
This happens only after the Sieve script that is executed for the corresponding message in the destination mailbox finishes running successfully.

Sieve extprograms plugin: Made line endings configurable for the input passed to the external program.

This was quite fundamentally broken, not only due to previous change.

It is still a plugin, but no longer a separate package.