Quelle:
https://apple.stackexchange.com/questions/12387/how-to-send-an-email-from-command-line

Configure Postfix for Gmail SMTP Edit file /etc/postfix/main.cf

sudo vim /etc/postfix/main.cf
and add in the following below the commented out relayhosts :-

relayhost = [smtp.gmail.com]:587
smtp_sasl_auth_enable = yes
smtp_sasl_password_maps = hash:/etc/postfix/sasl_passwd
smtp_sasl_security_options = noanonymous
smtp_use_tls = yes
Generate sasl_password if not already exists

sudo vim /etc/postfix/sasl_passwd
and enter in the following:-

[smtp.gmail.com]:587 username@gmail.com:password
Run the following commands

sudo chmod 600 /etc/postfix/sasl_passwd
sudo postmap /etc/postfix/sasl_passwd
sudo launchctl stop org.postfix.master
sudo launchctl start org.postfix.master
And you are done….
Now, you should be able to send emails from within the command line e.g. to send the contents of a directory as a tree to an email address

tree /var/www/somefolder | mail -s „contents“ your@yourdomain.com