Every once a while you need to send email from a Linux command line and there you go to google try to find it…

With attachment:

echo "message" | mailx -s "subject" -a attachment email@dress

echo "message" | mutt -s "subject" -a attachment -- email@dress

Without attachment:

echo "message" | mail -s "subject" email@ddress

Important:
Postfix by default restrict attachment size to approx 10MB i.e. 10240000 bytes.

You can check it using following command:

postconf | grep message_size_limit

To change attachment-size to say 50 MB, run a command like:

postconf -e message_size_limit=52428800