Spam – Who should prevent spammers from attacking Mailenable with external domain names?

We have a problem with our Mailenable, in which the MTA is activated in the MXSCAN software. Everything worked perfectly. Today, however, we found that we can only send emails but cannot receive them. We checked the logs in MxScan message logs when a stranger with an external IP and post office (null) and sender email (not from local domains) tries to send random emails every millisecond, and of course are blocked, we have blocked the IP for the incoming firewall rules as well, but still no impact that makes our mail activation so busy.Log screenshot