SMTP-outsourcing.rst

consumers: https://wiki.debian.org/Debate/DefaultMTA

ssmtp - no queue

• http://askubuntu.com/a/735071 see man for revaliases, or, better user msmtp

msmtp - no queue

• http://websistent.com/msmtp-cron/
• http://websistent.com/how-to-use-msmtp-with-gmail-yahoo-and-php-mail/ (2011)

nullmailer - has queue ?

• no local mail, 329192 -> Lacks mechanisms for responding to permanent failures, backing off retry frequency and timing out messages in the queue.
• https://opensourcehacker.com/2013/01/02/sendmail-using-nullmailer-and-gmail-account-on-linux-server/ (xinetd, 12.04)

other: https://wiki.debian.org/GmailAndExim4 issue: If you send a mail to a mailing list via a SMTP server provided by Gmail, the returned mail message from the mailing list is treated as read by the Gmail POP3 service

http://websistent.com/how-to-use-msmtp-with-gmail-yahoo-and-php-mail/ (smarthost vs satellite)

ssmtp (tested on jessie 8.6, stretch/sid)
fix for Debian bug #661954 - ssmtp.conf is world readable
had patch since 2014.01.28
This bug was known at least since 2008
FreeBSD solution since 2007.07.27

chown nobody:mail /usr/sbin/ssmtp /etc/ssmtp/ssmtp.conf 
chown root:mail /etc/ssmtp/revaliases /etc/ssmtp
chmod 2055 /usr/sbin/ssmtp
chmod 040 /etc/ssmtp/ssmtp.conf

https://github.com/KuJoe/Sendmail-to-SSMTP/blob/master/setup.sh
Mandrill example, additional params in ssmtp.conf

Elastic Email - impressed me with their API: https://api.elasticemail.com/public/help