Shell script to send mail via smtp : Send mail from external smtp server

You can use gmail or any other SMTP server as a smart host to send all messages from your Linux / UNIX desktop systems. You need to use a simple program called ssmtp. It accepts a mail stream on standard input with recipients specified on the command line and synchronously forwards the message to the mail transfer agent of a mailhub for the mailhub MTA to process.
Install ssmtp

# yum install ssmtp

Configure smarthost

# vi /etc/ssmtp/ssmtp.conf

Modify the following setting to setup SMTP mail server. Here, we have configured Google SMTP server to send mail.

AuthUser=replytosatya@gmail.com
AuthPass=***********
FromLineOverride=YES
mailhub=smtp.gmail.com:587
UseSTARTTLS=YES

Note: Before using this method to send mail, you need to disable sendmail.

# service sendmail stop

# chkconfig sendmail off

Now, you can use mail / mailx command to send email messages. You can also write a shell script to backup your files and email to somewhere else (see below). You can test settings using following syntax:

echo “This is a test” | mail -s “Test” satya@eduguru.in

Limittation of sSmtp:

sSMTP works well for desktop systems, but it is not a replacement for Sendmail / Postfix / Exim / Qmail for email server environment. This software is perfect for a single user system.