I have been using greylisting successfully for some time now, however over the last few days a few have been getting through. I am currently testing nolisting on one of my domains but in the meantime I noticed that out of the 10 spam that got through in the last week 8 were from a single IP range.
Plesk unfortunately does not provide any method to blacklist IP’s for the mail server. A little lateral thinking and I implemented it using the built in firewall. After the break you can see the settings I used for my qmail spammers rule.
I also did a scan through a couple of my other domains to find IP ranges that were responsible for more than 3 spam each and added those ranges as well. The 18.104.22.168 ip address sent 20 identical spam but no spam came from anywhere else in that /24 range so I only blocked the one IP address.
I will report back on the results.