Send command line server emails with Postfix on a Ubuntu Server 22.04

Here is a guide to allow a Ubuntu 22.04 server to send out local server based emails using Postfix.

Test Command Line Email

To test if emails can be sent via the command line, SSH into your server and try

echo "Is email sending OK..?" | mail -s "Sending email!" [email protected]

Nothing should return, if you do get a reply like the below, you are missing a mail utility package…

Command 'mail' not found, but can be installed with:

apt install mailutils

Then install mailutils and try again

apt install mailutils

Now there should be no output after the command is re-run, but the email may not arrive due to….. issues.

Try and get an idea by running a tail on the mail log.

tail -f /var/log/mail.log

or:

tail -f /var/log/syslog | grep postfix

Domain Name / FQDN

If your server has an invalid domain name the smtp connection will be rejected – set your server up with a valid domain name.

Firewall Port 25

If your smtp connection is timing out check that you have an outgoing Port 25 enabled, some providers will block this by default.

Reconfigure Postfix

If your server already has Postfix installed, of which most spun up servers already do you’ll most probably need to reconfigure Postfix with your correct domain name and sending parameters.

Postfix can be reconfigured using the command dpkg-reconfigure postfix, this will present a simple wizard which will ask a few questions.

dpkg-reconfigure postfix

• Configuration:  Internet Site
• System mail name: [server.example.com]
• Root and postmaster mail recipient: [blank]
• Destinations to accept mail for: server.example.com, server,  localhost.example.com, localhost
• Force synchronous updates on mail queue? No
• Local networks: 127.0.0.0/8 [::ffff:127.0.0.0]/104 [::1]/128
• Mailbox size limit (bytes): 0
• Local address extension character: +
• Internet protocols to use: all

After the wizard has finished check/edit 3 values…

nano /etc/postfix/main.cf

myhostname = server.example.com

mydestination = server.example.com, localhost.example.com, server, localhost

inet_interfaces = loopback-only

inet_interfaces will make sure it only receives email from local machine only, it sets the server to send email and only receive email from the loopback address.

Send Email from Main Domain

masquerade_domains = example.com

If your server has a subdomain or FQDN like server.example.com this will allow you to send email as the main domain, example.com – this directive is not in the main.cf file by default, add it in the end of the file if you want to use it.

postfix stop && postfix start

Restart the Postfix app

Alias System Emails

Set up an alias to receive email sent to the root account

nano /etc/aliases

and add …

root: [email protected]

Confirm the change…

newaliases

Test it works…

echo "Are you getting root's email  OK..?" | mail -s "Sending email!" root

Mail Relays

You can use a relay if you wish or if you have to because your IP address is blacklisted, there are many solutions with some providers offering a free tier account, 2 popular ones are SendGrid and MailGun.

That’s it, now you can send emails from the command line and receive roots email at another forwarded address.

Ref  &  Ref