I have several email accounts at different providers. Most of them don’t offer filtering capabilites like Sieve, or only their own non exportable rule system (Google Apps). My mail client of choice, Thunderbird, has filtering capabilities but my phone has not and I don’t want to leave my machine running Thunderbird all the time since it gets quite slow with huge mailboxes. Imapfilter is a mail filtering utility written in Lua which connects to one or more IMAP accounts and filters on the server using IMAP queries. It is a lightweight command line utility, the configuration can be versioned and is simple text and it is very fast.