How to Configure the ‘From’ Header in Cron Email Notifications Using msmtp on Linux


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When setting up cron jobs with msmtp as your MTA, you might encounter emails showing up as (unknown sender) in your Gmail inbox. The raw headers typically display:

From: root (Cron Daemon)

This occurs because msmtp inherits the system's default sender identity rather than using your configured email address.

First, ensure your ~/.msmtprc or /etc/msmtprc contains proper authentication:

defaults
auth on
tls on
tls_trust_file /etc/ssl/certs/ca-certificates.crt
logfile ~/.msmtp.log

account your_account
host smtp.gmail.com
port 587
from your.email@gmail.com
user your.email@gmail.com
password your_app_specific_password

1. Using msmtp's --from Flag

Modify your cron job to explicitly set the sender:

0 5 * * * /usr/bin/msmtp --from=your.name@domain.com -t recipient@domain.com < /path/to/your/script/output

2. System-wide MAILFROM Configuration

Create or edit /etc/email-addresses:

root: your.email@domain.com
www-data: your.email@domain.com

Then modify your msmtp configuration to use this file:

aliases /etc/email-addresses

For complete control, create a wrapper script (/usr/local/bin/sendmail-custom):

#!/bin/sh
/usr/bin/msmtp \
 --from="Your Name <your.email@domain.com>" \
 --add-missing-from-header \
 "$@"

Make it executable and update your symlink:

chmod +x /usr/local/bin/sendmail-custom
ln -sf /usr/local/bin/sendmail-custom /usr/sbin/sendmail

Test your configuration with:

echo "Test message" | mail -s "Test Subject" your.email@gmail.com

Check the resulting email headers to confirm the From address appears correctly.

When cron jobs send emails through msmtp, the default behavior is to use the system username (like 'root') as the sender, which gets flagged as (unknown sender) in email clients like Gmail. This happens because:

  • Cron uses the system's mail command format
  • msmtp inherits the envelope sender from the MTA
  • No proper email address is specified in the headers

1. Direct msmtp Configuration /h2>

Edit your ~/.msmtprc or /etc/msmtprc:

defaults
auth on
tls on
tls_trust_file /etc/ssl/certs/ca-certificates.crt
account your_account
host smtp.yourprovider.com
port 587
from your.email@example.com
user your_username
password your_password
account default : your_account

Key points:

  • The from field sets the default envelope sender
  • Make sure the file has correct permissions: chmod 600 ~/.msmtprc

2. Using mail.cf Wrapper /h2>

Create /usr/local/bin/mail.cf:

#!/bin/sh
/usr/bin/msmtp -t --from=your.email@example.com

Then make it executable and set as default:

chmod +x /usr/local/bin/mail.cf
sudo ln -sf /usr/local/bin/mail.cf /usr/sbin/sendmail

3. Cron MAILTO Directive /h2>

At the top of your crontab:

MAILTO="your.email@example.com"
SHELL=/bin/bash
PATH=/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin

# Then your jobs
* * * * * /path/to/your/script.sh

Verify with this command:

echo "Test message" | mail -s "Test Subject" your.email@example.com

Check the received email headers for proper 'From' field.

For complete control, use a script wrapper:

#!/bin/bash
{
    echo "From: Your Name <your.email@example.com>"
    echo "To: Recipient <recipient@example.com>"
    echo "Subject: Cron Job Notification"
    echo ""
    /path/to/your/script.sh
} | /usr/bin/msmtp -t

Remember to restart cron after changes: sudo service cron restart