Manage Sieve is a special mode used to display Sieve scripts available on a remote server. It can be invoked with M-x sieve-manage RET, which queries the user for a server and if necessary, user credentials to use.
When a server has been successfully contacted, the Manage Sieve buffer looks something like:
Server : mailserver:sieve 2 scripts on server, press RET on a script name edits it, or press RET on <new script> to create a new script. <new script> ACTIVE .sieve template.siv
One of the scripts are highlighted, and standard point navigation commands (<up>, <down> etc.) can be used to navigate the list.
The following commands are available in the Manage Sieve buffer: