msmtp

See also other alternatives

Configuration

/etc/msmtprc:

# Generics
defaults
auth           on
tls            on
# following is different from ssmtp:
tls_trust_file /etc/ssl/certs/ca-certificates.crt
# user specific log location, otherwise use /var/log/msmtp.log, however,
# this will create an access violation if you are user pi, and have not changes the access rights
logfile        /var/log/.msmtp.log

# Gmail specifics
account        gmail
host           smtp.gmail.com
port           587

from          root@raspi-buster
user           your-gmail-accountname@gmail.com
password       your-gmail-account-password

# Default
account default : gmail

Send an email

### cli

echo 'your message' | msmtp email@domain.tld

file

mail.txt

To:username@example.com
From:youraccount@gmail.com
Subject: Test

This is a test mail.

msmtp -t < mail.txt