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Sending mail with mu4e

Written by Solène, on 22 May 2018.
Tags: #unix #emacs

In my article about mu4e I said that I would write about sending mails with it. This will be the topic covered in this article.

There are a lot of ways to send mails with a lot of differents use cases. I will only cover a few of them, the documentation of mu4e and emacs are both very good, I will only give hints about some interestings setups.

I would thank Raphael who made me curious about differents ways of sending mails from mu4e and who pointed out some mu4e features I wasn’t aware of.

Send mails through your local server

The easiest way is to send mails through your local mail server (which should be OpenSMTPD by default if you are running OpenBSD). This only requires the following line to works in your ~/.emacs file:

(setq message-send-mail-function 'sendmail-send-it)

Basically, it would be only relayed to the recipient if your local mail is well configured, which is not the case for most servers. This requires a reverse DNS address correctly configured (assuming a static IP address), a SPF record in your DNS and a DKIM signing for outgoing mail. This is the minimum to be accepted to others SMTP servers. Usually people send mails from their personal computer and not from the mail server.

Configure OpenSMTPD to relay to another smtp server

We can bypass this problem by configuring our local SMTP server to relay our mails sent locally to another SMTP server using credentials for authentication.

This is pretty easy to set-up, by using the following /etc/mail/smtpd.conf configuration, just replace remoteserver by your server.

table aliases file:/etc/mail/aliases
table secrets file:/etc/mail/secrets

listen on lo0

accept for local alias <aliases> deliver to mbox
accept for any relay via secure+auth://label@remoteserver:465 auth <secrets>

You will have to create the file /etc/mail/secrets and add your credentials for authentication on the SMTP server.

From smtpd.conf(5) man page, as root:

# touch /etc/mail/secrets
# chmod 640 /etc/mail/secrets
# chown root:_smtpd /etc/mail/secrets
# echo "label username:password" > /etc/mail/secrets

Then, all mail sent from your computer will be relayed through your mail server. With ’sendmail-send-it, emacs will delivered the mail to your local server which will relay it to the outgoing SMTP server.

SMTP through SSH

One setup I like and I use is to relay the mails directly to the outgoing SMTP server, this requires no authentication except a SSH access to the remote server.

It requires the following emacs configuration in ~/.emacs:

(setq
  message-send-mail-function 'smtpmail-send-it
  smtpmail-smtp-server "localhost"
  smtpmail-smtp-service 2525)

The configuration tells emacs to connect to the SMTP server on localhost port 2525 to send the mails. Of course, no mail daemon runs on this port on the local machine, it requires the following ssh command to be able to send mails.

$ ssh -N -L 127.0.0.1:2525:127.0.0.1:25 remoteserver

This will bind the port 127.0.0.1:25 from the remote server point of view on your address 127.0.0.1:2525 from your computer point of view.

Your mail server should accept deliveries from local users of course.

SMTP authentication from emacs

It’s also possible to send mails from emacs using a regular smtp authentication directly from emacs. It is boring to setup, it requires putting credentials into a file named ~/.authinfo that it’s possible to encrypt using GPG but then it requires a wrapper to load it. It also requires to setup correctly the SMTP authentication. There are plenty of examples for this on the Internet, I don’t want to cover it.

Queuing mails for sending it later

Mu4e supports a very nice feature which is mail queueing from smtpmail emacs client. To enable it, it requires two easy steps:

In ~/.emacs:

(setq
  smtpmail-queue-mail t
  smtpmail-queue-dir "~/Mail/queue/cur")

In your shell:

$ mu mkdir ~/Mail/queue
$ touch ~/Mail/queue/.noindex

Then, mu4e will be aware of the queueing, in the home screen of mu4e, you will be able to switch from queuing to direct sending by pressing m and flushing the queue by pressing f.

Note: there is a bug (not sure it’s really a bug). When sending a mail into the queue, if your mail contains special characters, you will be asked to send it raw or to add a header containing the encoding.