zombie attack target email account

[djfininho]

Help please

a single email account is receiving around 30 to 50 emails from Undelivered Mail Returned to Sender
FROM: <MAILER-DAEMON@server.xxxxxxxxxxxx.xxx.xxx> TO: <xxxxxxxxx@xxxxxxxxxxxxxxx.xxxx.xxxx>
from different recipients.
but the email is not being used for sending, I believe it is a zombie attack, how to prevent sending emails using your email outside the server?

https://suporte.hostgator.com.br/hc/pt-br/articles/360015544414-O-que-é-um-ataque-de-e-mail-spoofing-

[overseer]

Are your SPF and DMARC DNS records set up properly to restrict sending to your own domain and server IP address?

[djfininho]

Are your SPF and DMARC DNS records set up properly to restrict sending to your own domain and server IP address?

hello overseer

Yes they are configured and validated

[overseer]

And have you hardened your postfix installation to prevent relaying? Pay particular attention to the $mynetworks and $relay_domains directives. Do you have UCE controls properly implemented in Postfix? Don't trust the defaults -- they are just a starting point. You should be much more restrictive than what CWP provides as an initial basis.

[djfininho]

And have you hardened your postfix installation to prevent relaying? Pay particular attention to the $mynetworks and $relay_domains directives. Do you have UCE controls properly implemented in Postfix? Don't trust the defaults -- they are just a starting point. You should be much more restrictive than what CWP provides as an initial basis.

Hello overseer.

Yes yes, and I am also monitoring more often.

Thank you for your attention.