Setup Email Notifications for Cron Jobs on Debian

How to set up email notifications for cron jobs on Debian 11 (Bullseye) using the msmtp SMTP email client.

Install msmtp

Install msmtp and msmtp-mta

apt-get install msmtp msmtp-mta

• msmtp is light SMTP email client that can be easily configured to forward emails to an SMTP server/email provider
• msmtp supports server profiles that can be used for sending mail to different email providers
• msmtp-mta creates an alias for sendmail, this means it can be used with any system that requires sendmail 

Create an aliases file

/etc/aliases is used by sendmail to redirect messages sent to local users/recipients to an email address

mailer-daemon - used for system messages about email issues
postmaster - the admin person who looks after email issues
root - redirect any emails sent to the root user
default - send everything else to this address

sudo nano /etc/aliases

mailer-daemon: email@domain.com
postmaster: email@domain.com
root: email@domain.com
default: email@domain.com 

Rebuild alias database

newaliases

Configure msmtp

sudo nano /etc/msmtprc

Send email using msmtp without authentication

This example creates a profile called smtp that will be used to send mail to an internal SMTP relay server that doesn't require authentication. The smtp profile is set as the default account.

# Set default values for all accounts
defaults
port 25
tls off
account smtp
host IP-ADDRESS
from EMAIL@DOMAIN.COM
auth off
# Set a default account
account default : smtp
# Aliases file
aliases /etc/aliases
 

Send email using msmtp to Office 365

This example creates a profile called o365 that will be used to send mail using Office 365

account o365
host smtp.office365.com
port 587
tls on
tls_starttls  on
tls_trust_file /etc/ssl/certs/ca-certificates.crt
auth on
from EMAIL@DOMAIN.COM
user EMAIL@DOMAIN.COM
password SECRET
# Set a default account
account default : o365
# Aliases file
 

sudo chown root:msmtp /etc/msmtprc
sudo chmod 640 /etc/msmtprc

Send a test email

Send a test email to an external address

echo "Test email using msmtp" | msmtp EMAIL@DOMAIN.COM

Send a test email to root

echo "Testing root email alias"| msmtp root

-v print debugging information for troubleshooting

echo "Testing root email alias"| msmtp -v root

Edit crontab

sudo crontab -e

Add this line at the top of the file to get email notifications from cron

MAILTO=EMAIL@DOMAIN.COM

References:

msmtp documentation
https://marlam.de/msmtp/documentation

Debian wiki msmtp
https://wiki.debian.org/msmtp

Debian manpages msmtp
https://manpages.debian.org/testing/msmtp/msmtp.1.en.html

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