VM provides general purpose marks that may be applied to any and all messages within a given folder. Certain VM commands can be subsequently invoked only on those message that are marked.
To mark the current message, type C-c C-@
(vm-mark-message). If you give a numeric prefix argument
n, the next n-1 messages will be marked as well. A negative
prefix argument means mark the previous n-1. An asterisk
(`*') will appear to the right of the message numbers of all marked
messages in the summary window.
To remove a mark from the current message, use C-c SPC
(vm-unmark-message. Prefix arguments work as with
vm-mark-message.
Use C-c C-a to mark all message in the current folder; C-c a removes marks from all messages.
To apply a VM command to all marked message you must prefix it with the
key sequence C-c RET (vm-next-command-uses-marks). The
next VM command will apply to all marked messages, provided the
command can be applied to such messages in a meaningful and useful way.
The current commands that can be applied to marked message are:
vm-delete-message, vm-discard-cached-data,
vm-followup, vm-followup-include-text, vm-reply,
vm-reply-include-text, vm-save-message,
vm-save-message-sans-headers, vm-send-digest,
vm-undelete-message, and vm-unread-message.