This page contains several '''lightweight''' SMTP agents (see MailConcept)
which you can call from mutt via the "`$sendmail`" variable,
if you think that a full blown sendmail/postfix/qmail is overkill.
Note, on most systems an MTA is already installed to process system-mail, so you might not need to mess around with yourself (maybe if you want to bypass defaults)

Feel free to add your comments so that others can make a better decision which one to choose.

 * nullclient (http://www.postfix.org/, http://www.sendmail.org/)
  * sendmail can be configured to simply pass on all mail and do nothing else fancy, see '''nullclient''' feature in cf/README or postfix-doc.
  * This ''might'' save you an installation of extra software, since sendmail or postfix is installed by default on many systems.

 * ssmtp (http://packages.debian.org/testing/mail/ssmtp.html)
  * Manual is in the source tarball. Supports TLS, IPv6 and MD5-auth. Optionally rewrites From: header.
  * SMTP Password has to be saved in a configuration file. No comandline authentification possible.
 * nullmailer http://untroubled.org/nullmailer/
  * Supports SMTP AUTH PLAIN as of 1.02. No SSL.
 * nomail (http://www.luky.org/opensrc/nomail/)
  * Can rewrite From, delete Message-ID, receive mail for local users, and handle aliases, queueing.
  * Supports IPv6 if you apply http://www.ku3g.org/negi/nomail/nomail-ipv6.patch .
 * nbsmtp (http://nbsmtp.ferdyx.org/)
  * Supports TLS, SYSLOG, SASL, IPv6, STARTTLS, no need to configure it even though it supports a config file.
 * esmtp (http://esmtp.sourceforge.net/)
  * supports AUTH SMTP extension, with the CRAM-MD5 and NTLM SASL mechanisms, StartTLS SMTP extension
  * fully sendmail command line compatible, feature that autochooses the server according to `$from`
 * msmtp (http://msmtp.sourceforge.net/)
  * Supports TLS, IPv6, DSN, various authentication methods. One-line-configuration in .muttrc; feature that autochooses the server according to `$from`.
  * SMTP Password has to be saved in a configuration file. No comandline authentification possible.
  * IMPORTANT! will refuse to send your mail if you've tls in your ~/.msmtprc and SMTP server has TLS certificate that you don't trust.
   * To get around this, either trust the certificate, or you can add tls_nocertcheck to your ~/.msmtprc.
 * mini_sendmail (http://www.acme.com/software/mini_sendmail/)
  * `set sendmail="mini_sendmail -t -ssmtpserver" ; unset $use_envelope_from`
  * no space between -s and smtpserver, supports IPv6, no support for smtp authentification.
 * masqmail (http://innominate.org/kurth/masqmail/)
  * Not really lightweight, a full MTA, depends on Glib (no, not Gtk)
 * smtppush(.py) (http://jclement.ca/software/smtppush.py/)
  * A cross-platform clone of Michael Elkins' SMTPPUSH program.
 * sendmail(.py) (http://www.ynform.org/w/Pub/SendmailPy)
  * A python script, compatible with mutt, which uses the most secure channel it can find
 * Putmail (http://putmail.sourceforge.net/)
  * Simple configuration, Multiplatform. Written in Python. Optional specific settings depending on the "From:" header.
  * Supports SMTP authentication, TLS and IPv6 and has an optional, simple queuing system.
 * DMA (!DragonFly Mail Agent, http://packages.debian.org/de/sid/dma)
  * TLS/SSL and SMTP authentication, /etc/dma/{dma.conf,auth.conf,virtusertable}
  * set sendmail="/usr/sbin/dma -Ac -i"
 * Exim (http://www.exim.org/)
  * Exim is a full-blown MTA, but has a configuration option (mua_wrapper) to behave as a simple non-queuing SMTP client.
  * http://www.exim.org/exim-html-current/doc/html/spec_html/ch48.html

 * ssh: if you don't have local agent but want to use on remote site.
  * `'set sendmail="ssh remotehost sendmail ..."'`
  * authentification (optional only once) possible with ssh keys; won't work with all systems, you can't reach all smtp servers with ssh.