A somewhat longer configuration, showing some more things that you can customize.
;; example configuration for mu4e
(require 'mu4e)
;; use mu4e for e-mail in emacs
(setq mail-user-agent 'mu4e-user-agent)
;; the next are relative to the root maildir
;; (see `mu info`).
;; instead of strings, they can be functions too, see
;; their docstring or the chapter 'Dynamic folders'
(setq mu4e-sent-folder "/sent"
mu4e-drafts-folder "/drafts"
mu4e-trash-folder "/trash")
;; the maildirs you use frequently; access them with 'j' ('jump')
(setq mu4e-maildir-shortcuts
'((:maildir "/archive" :key ?a)
(:maildir "/inbox" :key ?i)
(:maildir "/work" :key ?w)
(:maildir "/sent" :key ?s)))
;; the headers to show in the headers list -- a pair of a field
;; and its width, with `nil' meaning 'unlimited'
;; (better only use that for the last field.
;; These are the defaults:
(setq mu4e-headers-fields
'( (:date . 25) ;; alternatively, use :human-date
(:flags . 6)
(:from . 22)
(:subject . nil))) ;; alternatively, use :thread-subject
(add-to-list 'mu4e-bookmarks
;; ':favorite t' i.e, use this one for the modeline
'(:query "maildir:/inbox" :name "Inbox" :key ?i :favorite t))
;; program to get mail; alternatives are 'fetchmail', 'getmail'
;; isync or your own shellscript. called when 'U' is pressed in
;; main view.
;; If you get your mail without an explicit command,
;; use "true" for the command (this is the default)
(setq mu4e-get-mail-command "offlineimap")
;; general emacs mail settings; used when composing e-mail
;; the non-mu4e-* stuff is inherited from emacs/message-mode
(setq mu4e-compose-reply-to-address "foo@bar.example.com"
user-mail-address "foo@bar.example.com"
user-full-name "Foo X. Bar")
(setq message-signature "Foo X. Bar\nhttp://www.example.com\n")
;; smtp mail setting
(setq
message-send-mail-function 'smtpmail-send-it
smtpmail-default-smtp-server "smtp.example.com"
smtpmail-smtp-server "smtp.example.com"
smtpmail-local-domain "example.com"
;; if you need offline mode, set these -- and create the queue dir
;; with 'mu mkdir', i.e.. mu mkdir /home/user/Maildir/queue
smtpmail-queue-mail nil
smtpmail-queue-dir "/home/user/Maildir/queue/cur")
;; don't keep message buffers around
(setq message-kill-buffer-on-exit t)