8.2 What to mark for

mu4e supports a number of marks:

mark for/as  | keybinding  | description
-------------+-------------+------------------------------
delete       | D, <delete> | delete
move         | m           | move to some maildir
refile       | r           | mark for refiling
-------------+-------------+------------------------------
flag         | +           | mark as 'flagged' ('starred')
unflag       | -           | remove 'flagged' mark
read         | !           | mark as read
unread       | ?           | marks as unread
trash        | d           | move to the trash folder
untrash      | =           | remove 'trash' flag
-------------+-------------+------------------------------
label        | l           | change the labels
unlabel      | L           | clear all labels
action       | a           | apply some action
'something'  | *, <insert> | mark now, decide later
-------------+-------------------------------------------
unmark       | u           | remove mark at point
unmark all   | U           | remove all marks
-------------+-------------------------------------------