ターミナルからメールを送信する

sudo apt install ssmtp

#
# Config file for sSMTP sendmail
#
# The person who gets all mail for userids < 1000
# Make this empty to disable rewriting.
#root=postmaster
root=myemail@hoge.com

# 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=mail
mailhub=smtp.hoge.com:587

AuthUser=myemail@hoge.com
AuthPass=*****
UseTLS=YES
UseSTARTTLS=YES

# Where will the mail seem to come from?
#rewriteDomain=
rewriteDomain=hoge.com

# The full hostname
#hostname=
hostname=MyServer

# 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

$ vim testmail.txt
testmail.txt
To: recieve@hoge.com
From: myemail@hoge.com
Subject: ssmtp test

Test message.

$ sendmail -t < testmail.txt

もしくは

$ ssmtp recieve@hoge.com < testmail.txt