Masquerade email address

If you have followed Outgoing main via Gmail or Enable Outgoing Emails tutorial, you will notice that the sending email address is not properly formed. For example, it appears as root@hda.amahi.net vs root@amahi.net. This can be easily changed with a minor update to Postfix.

You can force Postfix to send local emails with your preferred email address as the "sender" header. This means that when you send mails using "mail" or mails automatically sent by root,you can get your email at the from field.

• Open terminal as root, create /etc/postfix/sender_canonical file:

vi /etc/postfix/sender_canonical

• Create the /etc/postfix/sender_canonical, and add user -> email references like this:

root         admin@yourisp.com
logwatch     logwatch@yourisp.com

• Create /etc/postfix/sender_canonical.db file:

postmap hash:/etc/postfix/sender_canonical

• Add sender_canonical variable to /etc/postfix/main.cf:

postconf -e "sender_canonical_maps=hash:/etc/postfix/sender_canonical"

• Restart postfix:

systemctl restart postfix.service

REF: Make Postfix rewrite sender header on local mails