SSMTP

sudo apt install ssmtp

thierry@binova-srv:~$ whereis sendmail
sendmail: /usr/sbin/sendmail /usr/lib/sendmail /usr/share/man/man8/sendmail.8.gz
thierry@binova-srv:~$ ls -la /usr/sbin/sendmail
lrwxrwxrwx 1 root root 5 avril  3  2018 /usr/sbin/sendmail -> ssmtp

/etc/ssmtp/ssmtp.conf

#
# Config file for sSMTP sendmail
#
# The person who gets all mail for userids < 1000
# Make this empty to disable rewriting.
root=servers@linformatic.fr
AuthUser=servers@linformatic.fr
AuthPass=xxXXxxXX
 
# The place where the mail goes. The actual machine name is required no
# MX records are consulted. Commonly mailhosts are named mail.domain.com
mailhub=ssl0.ovh.net:465
UseTLS=YES
 
# Where will the mail seem to come from?
#rewriteDomain=
 
# The full hostname
hostname=binova-srv@binova.lan
 
# Are users allowed to set their own From: address?
# YES - Allow the user to specify their own From: address
# NO - Use the system generated From: address
#FromLineOverride=YES

• http://tombuntu.com/index.php/2008/10/21/sending-email-from-your-system-with-ssmtp/