There is Front Door Rejector function to reject invalid recipients,also it can use to blocked sender,but all return with error: 550 No such user found on the system. (CRF)

if sender rejected can be independent config file,reject with error message such as: Sender email or domain rejected by the system. I think it will be better.

SenderRejection.dat
[\S]*@outlook\.jp$$$ALL

Rejected with message: Sender email or domain rejected by the system.

CustomRejection.dat
ALL$$$no_such_persion@mydomain.com
spammerTwo@nono.com$$$validuser@yourdomain.com

Rejected with message: 550 No such user found on the system or rejected by recipents.

There are too many outlook.jp spams,even to quarantined is wasting disk space.

By the way,if AttackerIP.txt can support ip range,it will be much better. At the moment,it seems only support single IP

Such as

11.22.33.0/24

22.33.20.0/16

All of the "Front Door Rejectors" should only be used as a last resort. These filters reject incoming emails right away and therefore, it will be very difficult to troubleshoot if something goes wrong. We have had instances in the past where folks call our support department because they added someone either incorrectly or forgot about it and now there is no trace of the connection.

If you're getting hit by someone trying to guess passwords, make sure you disable SMTP Authentication for the primary port (25) and check Block Malicious IP Addresses under Server Configuration/Advance tab. This will automatically block IP addresses temporarily.