Sending System E-mails with Gmail

Here's how to send system mails from your computer using a gmail account:

Assuming apt-based package manager, remove sendmail (overkill and bloated for our use) and install ssmtp:

apt-get remove sendmail*
apt-get install ssmtp

Log in to gmail and create an application password for authentication: https://myaccount.google.com/apppasswords In this example, the application password is:

sdfsdfgadfgdfsdf

In your /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=myusername@gmail.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=smtp.gmail.com:587
 
AuthUser=myusername@gmail.com
AuthPass=sdfsdfgadfgdfsdf

UseSTARTTLS=yes
UseTLS=yes

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

# The full hostname
hostname=mydomain.com

# 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

Note: The rewriteDomain and hostname options don't really work... gmail always replaces the From address with your gmail address :-(

For the examples below, let's assume the following:

• Your gmail address is: myusername@gmail.com
• Your local system's hostname is: mycomputer.mydomain.com
• Your local system username is: jeremy
• You will send a test email to Bob Ross <bobross@happytrees.com>

Adjust each of those and anything in red as needed.

Edit your /etc/ssmtp/revaliases, add a line for any local user for which you would like to have all mail redirected elsewhere.

jeremy:myusername@gmail.com:smtp.gmail.com:587

You should have the following in /etc/hosts:

mycomputer.mydomain.com

You should have the following in /etc/hosts

127.0.1.1 mycomputer.mydomain.com

Test sending an email to Bob Ross via bobross@happytrees.com with:

echo -e "To: Bob Ross <bobross@happytrees.com>\r\nSubject: Email test at $(date) from $(hostname)\r\n\r\ntesting..."  | sendmail jeremy

This results in the following email:

Bcc: jeremy@mydomain.com
Return-Path: <myusername@gmail.com>
Received: from mycomputer.mydomain.com ([2603:3020:2ff0:c000::1874])
        by smtp.gmail.com with ESMTPSA id f17sm2049437uaq.19.2020.01.24.21.38.52
        for <jeremy@mydomain.com>
        (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256);
        Fri, 24 Jan 2020 21:38:54 -0800 (PST)
Message-ID: <5e2bd46e.1c69fb81.b7332.d795@mx.google.com>
Received: by mycomputer.mydomain.com (sSMTP sendmail emulation); Sat, 25 Jan 2020 00:38:52 -0500
From: root <myusername@gmail.com>
Date: Sat, 25 Jan 2020 00:38:52 -0500
To: Bob Ross <bobross@happytrees.com>
Subject: Email test at Sat Jan 25 00:38:52 EST 2020 from mycomputer.mydomain.com

testing...

Which appears like so in your inbox:

from:      root <myusername@gmail.com>
to:        Bob Ross <bobross@happytrees.com>
bcc:       jeremy@mydomain.com
date:      Jan 25, 2020, 12:38 AM
subject:   Email test at Sat Jan 25 00:38:52 EST 2020 from mycomputer.mydomain.com
mailed-by: gmail.com

You can then create an email filter for organizing those emails. Create a filter with the To: field. You can use either the Bcc: address above (jeremy@mydomain.com) or the To: address (Bob Ross <bobross@happytrees.com>).

I use the following filter convention so that I can filter by domain name, computer name, and user name:

• Email format
  • To: field: jeremy@mycomputer.mydomain.com
• Gmail Filter
  • To: jeremy@mycomputer.mydomain.com
  • Label Name: Systems/mycomputer.mydomain.com/jeremy

For example, you may have the following addresses:

• jeremy@desktop.home.mydomain.com
• apache@desktop.home.mydomain.com
• jeremy@notebook.office.mydomain.com
• root@firewall.home.mydomain.com
• root@freenas.home.mydomain.com

Even though gmail delivers them to your gmail address (myusername@gmail.com), you can still filter based on the original To: or system (Bcc:) address.