View source for 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:
 <font color=red>sdfsdfgadfgdfsdf</font>

In your <tt>/etc/ssmtp/ssmtp.conf</tt>:
 #
 # Config file for sSMTP sendmail
 #
 # The person who gets all mail for userids < 1000
 # Make this empty to disable rewriting.
 root=<font color=red>myusername@gmail.com</font>
 
 # 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=<font color=red>smtp.gmail.com:587</font>
  
 AuthUser=<font color=red>myusername@gmail.com</font>
 AuthPass=<font color=red>sdfsdfgadfgdfsdf</font>
 
 UseSTARTTLS=<font color=red>yes</font>
 UseTLS=<font color=red>yes</font>
 
 # Where will the mail seem to come from?
 rewriteDomain=<font color=red>mydomain.com</font>
 
 # The full hostname
 hostname=<font color=red>mydomain.com</font>
 
 # 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=<font color=red>YES</font>


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: <font color=red>myusername@gmail.com</font>
* Your local system's hostname is: <font color=red>mycomputer.mydomain.com</font>
* Your local system username is: <font color=red>jeremy</font>
* You will send a test email to <font color=red>Bob Ross <bobross@happytrees.com></font>
Adjust each of those and anything in red as needed.

Edit your <tt>/etc/ssmtp/revaliases</tt>, add a line for any local user for which you would like to have all mail redirected elsewhere.
 <font color=red>jeremy</font>:<font color=red>myusername@gmail.com</font>:smtp.gmail.com:587

You should have the following in <tt>/etc/hosts</tt>:
 <font color=red>mycomputer.mydomain.com</font>

You should have the following in <tt>/etc/hosts</tt>
 127.0.1.1 <font color=red>mycomputer.mydomain.com</font>

Test sending an email to <font color=red>Bob Ross via bobross@happytrees.com</font> with:
 echo -e "To: <font color=red>Bob Ross <bobross@happytrees.com></font>\r\nSubject: Email test at $(date) from $(hostname)\r\n\r\ntesting..."  | sendmail jeremy

This results in the following email:
 Bcc: <font color=red>jeremy@mydomain.com</font>
 Return-Path: <<font color=red>myusername@gmail.com</font>>
 Received: from <font color=red>mycomputer.mydomain.com</font> ([2603:3020:2ff0:c000::1874])
         by smtp.gmail.com with ESMTPSA id f17sm2049437uaq.19.2020.01.24.21.38.52
         for <<font color=red>jeremy@mydomain.com</font>>
         (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 <font color=red>mycomputer.mydomain.com</font> (sSMTP sendmail emulation); Sat, 25 Jan 2020 00:38:52 -0500
 From: root <<font color=red>myusername@gmail.com</font>>
 Date: Sat, 25 Jan 2020 00:38:52 -0500
 To: <font color=red>Bob Ross <bobross@happytrees.com></font>
 Subject: Email test at Sat Jan 25 00:38:52 EST 2020 from <font color=red>mycomputer.mydomain.com</font>
 
 testing...

Which appears like so in your inbox:
 from:      root <<font color=red>myusername@gmail.com</font>>
 to:        <font color=red>Bob Ross <bobross@happytrees.com></font>
 bcc:       <font color=red>jeremy@mydomain.com</font>
 date:      Jan 25, 2020, 12:38 AM
 subject:   Email test at Sat Jan 25 00:38:52 EST 2020 from <font color=red>mycomputer.mydomain.com</font>
 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 (<font color=red>jeremy@mydomain.com</font>) or the To: address (<font color=red>Bob Ross <bobross@happytrees.com></font>).

I use the following filter convention so that I can filter by domain name, computer name, and user name:
* Email format
** To: field: <font color=red>jeremy@mycomputer.mydomain.com</font>
* Gmail Filter
** To: <font color=red>jeremy@mycomputer.mydomain.com</font>
** Label Name: Systems/<font color=red>mycomputer.mydomain.com</font>/<font color=red>jeremy</font>

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 (<font color=red>myusername@gmail.com</font>), you can still filter based on the original To: or system (Bcc:) address.