You can find most things you can do with this message in the Mu4e menu, or by using the keyboard; the default bindings are:
key description ============================================================== n,p view the next, previous message ],[ move to the next, previous unread message y select the headers view (if it's visible) RET scroll down M-RET open URL at point / attachment at point SPC scroll down, if at end, move to next message S-SPC scroll up searching --------- s search S edit last query / narrow the search b search bookmark B edit bookmark before search j jump to maildir M-left previous query M-right next query marking messages ---------------- d mark for moving to the trash folder = mark for removing trash flag ('untrash') DEL,D mark for complete deletion m mark for moving to another maildir folder r mark for refiling +,- mark for flagging/unflagging u unmark message at point U unmark *all* messages % mark based on a regular expression T,t mark whole thread, subthread <insert>,* mark for 'something' (decide later) # resolve deferred 'something' marks x execute actions for the marked messages composition ----------- R,F,C reply/forward/compose E edit (only allowed for draft messages) actions ------- g go to (visit) numbered URL (using `browse-url') (or: <mouse-1> or M-RET with point on url) C-u g visits multiple URLs f fetch (download )the numbered URL. C-u f fetches multiple URLs k save the numbered URL in the kill-ring. C-u k saves multiple URLs e extract (save) one or more attachments (asks for numbers) (or: <mouse-2> or S-RET with point on attachment) a execute some custom action on the message A execute some custom action on the message's MIME-parts misc ---- ; switch context . show the raw message view. 'q' takes you back. C-+,C-- increase / decrease the number of headers shown H get help C-S-u update mail & reindex q leave the message view
For the marking commands, please refer to Marking messages.