Error solution : -
Check port in
- Incoming mail
- Outgoing mail
A check on Port Incoming mail, Outgoing mail and server same ‘mail.example.com’ or ‘stmp.gmail.com’ .
$ sudo nano /etc/postfix/main.cf
myhostname = ns1.example.com
alias_maps = hash:/etc/aliases
mynetworks = 127.0.0.0/8 [::ffff:127.0.0.0]/104 [::1]/128 your IP
- Restart Postfix
$ sudo systemctl restart postfix