A library for parsing, sorting and filtering your mail.
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. libSieve makes no attempt to 
have knowledge of how SMTP, IMAP, or anything else work; just how to 
parse and deal with a buffer full of emails. The rest is up to you!