If you cannot send mail right now, for example because you are currently offline, you can queue the mail, and send it when you have restored your internet connection. You can control this from The main view.
To allow for queuing, you need to tell smtpmail where you want to store
the queued messages.
For convenience, we put the queue directory somewhere in our normal maildir. If
you want to use queued mail, you should create this directory before
starting mu4e. The mu mkdir command may be useful here, so for
example:
$ mu mkdir ~/Maildir/queue $ touch ~/Maildir/queue/.noindex
The file created by the touch command tells mu to ignore this
directory for indexing, which makes sense since it contains smtpmail
meta-data rather than normal messages; see the mu-mkdir and mu-index
man-pages for details.
Then, tell smtpmail about it; e.g., in your configuration:
(setq smtpmail-queue-mail nil ;; use t to start in queuing mode
smtpmail-queue-dir "~/Maildir/queue/cur"
;; or nil to disable queuing
)
Once you are ready to send your messages, you can invoke M-x smtpmail-send-queued-mail.
Warning: when you switch on queued-mode, your messages won’t reach
their destination until you ; so, be careful not to do this
accidentally! If you want to avoid queued mode completely, you can set
smtpmail-queue-dir to nil.