Version 2.3.1 is available upstream. Please consider updating!
It seems that version 2.3.1 is available upstream, while the latest version in the Gentoo tree is 2.2.7. You think this warning is false? Read more about it here.
libSieve provides a library to interpret Sieve scripts, and to execute those
scripts over a given set of messages. The return codes from the libSieve
functions let your program know how to handle the message, and then it's up to
you to make it so.