The current version of Sieve's base specification is outlined in RFC 5228, published in January 2008.
While Sieve has many limitations – the base standard has no variables and no loops – it does allow conditional branching, preventing runaway programs.
Although extensions have been devised to extend the language to include variables and, limited loops, the language is still highly restricted, and thus suitable for running user-devised programs as part of the mail system.
The ManageSieve protocol (defined in RFC 5804) allows users to manage their Sieve scripts on a remote server.
The IETF Sieve working group[5] has updated the base specification in 2008 (RFC 5228), and has brought the following extensions to Proposed Standard status: A number of other extensions are still being developed by the Sieve working group.