Plesk Anti-Spam Features
Plesk provides a number of anti-spam features
- Spamassassin
- Greylisting
- SPF Blocks
- Email White Lists
- Email Black lists
In this 2 minute video, I cover how to set up Spamassassin and enable some DNS real-time blacklists to help you reduce the spam coming into your Plesk server.
2 Minute Tutorial: Setting Up Spamassassin & Blacklists on Plesk
Spamassassin Settings
These are the three settings to check:
I recommend you enable the first box which turns on spam filtering using Spamassassin. This will not delete any email but tag emails as spam for you.
The second options uses greylisting. Basically, greylisting rejects an email if it has not recently seen an email from the IP address. The rejection is a soft failure. Most legitimate email servers will try again in 15-60 minutes. When the sending server tries to deliver the email again, the email your server will permit the email..
Greylisting can cause issues when receiving password reset forms, invoice notifications and similar notices. If the sending IP is not known, then the password reset or other notice is delayed – which can cause your users a lot of frustration. So unless the other tips are not working, you may want to leave this off.
The last box allows you to customize spam settings on a per-domain basis. This is really up to you. In general, if your users are not technically savvy, I would uncheck this box. They could easily setup scores that could block legitimate email.
Blacklist Settings in Plesk
To setup real-time DNS blacklists in Plesk, go to the Mail Server Settings page:
You can select any blacklists you want, but I recommend the following:
Spamhaus XBL Advisory List
The Spamhaus Exploits Block List (XBL) is a realtime database of IP addresses of hijacked PCs infected by illegal 3rd party exploits, including open proxies (HTTP, socks, AnalogX, wingate, etc), worms/viruses with built-in spam engines, and other types of trojan-horse exploits.
This is a very effective list and it includes the popular CBL abuseseat list which I find effective as well.
To enable this list use:
xbl.spamhaus.org
Barracuda Reputation Block List (BRBL)
The BRBL is open to public and can be used within reason. Barracuda Networks is currently making this service available free of charge and we hope to keep it that way.
This list scores among the top of the Blacklist Compared site which ranks DNS RBLs.
To enable this list use:
b.barracudacentral.org
Those are the two lists I recommend to start. There are plenty of others but some have very high false positive rates.
Better Spam Filtering
For better spam filtering, you really need to turn to dedicated 3rd party filtering tools. We use McAfee SaaS Email Inbound Filtering services but there are many others.