Sometimes it is desirable to perform an operation on a group of messages all at once rather than one at a time. An example might be to save messages to a mailing list to a separate folder, or to delete all messages with a given subject. To tag all messages matching a pattern, use the tag-pattern function, which is bound to ``shift-T'' by default. Or you can select individual messages by hand using the ``tag-message'' function, which is bound to ``t'' by default. See patterns for Mutt's pattern matching syntax.
Once you have tagged the desired messages, you can use the ``tag-prefix'' operator, which is the ``;'' (semicolon) key by default. When the ``tag-prefix'' operator is used, the next operation will be applied to all tagged messages if that operation can be used in that manner. If the $auto_tag variable is set, the next operation applies to the tagged messages automatically, without requiring the ``tag-prefix''.