This is sieve-connect. A client for the ManageSieve protocol, as specifed in RFC 5804. Historically, this was MANAGESIEVE as implemented by timsieved in Cyrus IMAP. This software is licensed and the terms are provided in the file "LICENSE" as supplied with this software (BSD license without the advertising clause). SIEVE is an RFC-specified language for mail filtering, which at time of writing is specified in a list of RFCs at the end of this document, plus various drafts, both IETF and individual submissions. It's designed to be regular enough for machines to be able to manipulate, whilst still being editable by humans. Alas, not many clients actually implement this instead of embedding their own internal codes in sieve comments, defeating the goal of being able to edit with a client of your choice. This is not yet fully compatible with RFC 5804, but is moving towards that from the timsieved baseline; some issues to be worked on are documented in the "TODO" file. sieve-connect speaks ManageSieve and supports TLS for connection privacy and also authentication if using client certificates. sieve-connect will use SASL authentication; SASL integrity layers are not supported, use TLS instead. GSSAPI-based authentication should generally work, provided that client and server can use a common underlaying protocol. If it doesn't work for you, please report the issue. sieve-connect is designed to be both a tool which can be invoked from scripts and also a decent interactive client. It should also be a drop-in replacement for "sieveshell", as supplied with Cyrus IMAP.