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.