Setup mail command in linux

Supposing we have sendmail in the linux server, the easiest way to setup any server without a valid FDQN hostname is using msmtp:

apt-get install msmtp msmtp-mta mailutils

If used by root, create the file

nano /etc/msmtprc

Otherwise, create a local file

nano ~/.msmtprc

Inside, paste the configuration you need, specifically, the original email address used by the “from” field

# Set default values for all following accounts.
defaults

# Set the mail server port.
port 587

# Use TLS.
tls on

# Use system certificates
tls_trust_file /etc/ssl/certs/ca-certificates.crt

# Mail account
account xxx@vvvvvv.com

# SMTP server
host smtp.mail.com

# Envelope-from address
from xxx@vvvvvv.com

# Authentication. The password is given using one of five methods, see below.
auth on

# user name for mail server
user xxx@vvvvvv.com

password superpassword

# Set a default account
account default: xxx@vvvvvv.com

# Map local users to mail addresses (for crontab)
aliases /etc/aliases

For services like sendgrid, the above configuration worked, for using 1&1 / Ionos, following line is needed:

set_from_header on

After editing, set the correct permissions on the file:

chmod 600 /etc/msmtprc

chmod 600 ~/.msmtprc

For fallback addresses, it's needed to update the /etc/aliases file

root: xxx@vvvvvv.com
default: xxx@vvvvvv.com

At the end, we need to tell sendmail to use msmtp, edit the /etc/mail.rc file:

set sendmail="/usr/bin/msmtp -t"

To test, you can send an email like this:

echo "hello world" | mail -s "test email" foo@bar.com

Extra: if your application is throwing an error, saying “sendmail: account default not found” or something like that, verify that the user belongs to the “msmtp” group and check that the binary is correct:

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