Your generic file should have the below entries:
root [email protected]
root@localhost [email protected]
[email protected] [email protected]
root@freepbx [email protected]
[email protected] [email protected]
asterisk [email protected]
asterisk@localhost [email protected]
[email protected] [email protected]
asterisk@freepbx [email protected]
[email protected] [email protected]
[email protected] [email protected]
vm@asterisk [email protected]
Note that in place of [email protected] should be the email you want to send from, and the one entry with [email protected] you should replace with your fqdn.
Postfix configurations normally persist through module and OS upgrades, but always good to have a backup.