smailq

Smailq is a mail queue for lightweight SMTP clients (MSAs) like msmtp that do not feature a queue. Smailq basically provides the functionality of sendmail and mailq.

Use case. A typical use case is the following: You have a notebook or a workstation without a full-fledged MTA (e.g., postfix) installed, but something like msmtp, esmtp, or ssmtp, which only forward the mail to an SMTP server. Such lightweight SMTP clients typically do not feature a mail queue.1 In case that your SMTP client cannot connect to the SMTP server, the mail is lost2.

Smailq implements a mail queue and uses MSAs like msmtp to actually deliver mails. It also comes with shell scripts sendmail and mailq that wrap around smailq. Note that typical Unix-type software (e.g., cron, caff, etc.) uses /usr/sbin/sendmail to send mails. Hence, if cron informs the administrator of an error while the notebook is offline, the mail is inserted into the queue instead of being dropped.

Usage

$ smailq -h

smailq is a mail queue for lightweight SMTP clients (MSAs) like msmtp that do
not provide a queue. It basically provides the functionality of sendmail and
mailq.

USAGE:

  /usr/bin/smailq --send [recipient ...] -- [MSA options ...]
  /usr/bin/smailq --list
  /usr/bin/smailq --deliver-all
  /usr/bin/smailq --deliver [ID ...]
  /usr/bin/smailq --delete [ID ...]
  /usr/bin/smailq --help
  /usr/bin/smailq --version

COMMANDS:

      --delete
          Remove the mails with given IDs from the queue.

      --deliver
          Attempt to deliver the mails with given IDs only.

      --deliver-all
          Attempt to deliver all mails in the queue.

  -h, --help
          Print this usage text.

      --list
          List all mails in the queue. This is the default

      --send
          Read a mail from stdin, insert it into the queue, and attempt to
          deliver all mails in the queue. Options after "--" are passed forward
          to the MSA for this particular mail.

  -V, --version
          Show version info.

OPTIONS:

  -C, --config=FILE
          Use the given configuration file instead of "$HOME/.smailq.conf".

  -q, --quiet
          Do not print info messages.

  -v, --verbose
          Increase output verbosity.

Configuration file

By default, smailq looks at $HOME/.smailq.conf and /etc/smailq.conf (in that order) for a configuration file, unless the configuration file is explicitly specified by an option. A configuration file with its default values would look like this:

[general]
# Optional: The directory where the log file is written to. The special
# value 'syslog' causes smailq to log to syslog.
logdir = ~/.smailq/log/
# Optional: The directory where smailq saves the mail queue data
datadir = ~/.smailq/data/

# Settings for the network (TCP) connectivity test
[nwtest]
# Optional: The host to connect to
host = www.google.com
# Optional: The port to connect to
port = 80
# Optional: The timeout
timeout = 8

# Settings concerning the mail submission agent
[msa]
# This command is called when smailq attempts to deliver a mail. The
# MSA-options passed to smailq are appended to this line.
cmd = /usr/bin/msmtp

Download

You may obtain a copy of the git repository of smailq by

$ git clone https://git.sthu.org/repos/smailq.git

or you can simply download the latest tarball.

Installation

Installation is done by simply calling make install in the source directory as a privileged user.

If you use Gentoo Linux, then you may get a copy of my Gentoo overlay. Besides mail-mta/smail, the overlay also contains a virtual/mta ebuild that takes smailq into account. If some package is depending on an mta, Gentoo portage will enforce that virtual/mta is installed, which will again pull-in a concrete package that provides /usr/sbin/sendmail. This would lead to a conflict when installing smailq by hand. Hence, it is recommended to use the respective ebuilds.

  1. msmtp for instance ships shell scripts that implement a simple queuing mechanism around msmtp. However, /usr/sbin/sendmail is still a symlink to /usr/bin/msmtp and, thereby, Unix-type software like cron would trust that msmtp queues mails that cannot be delivered right now. ↩

  2. It would be the responsibility of the caller of the SMTP client to queue mails, which is typically not the case. ↩