ASSP is one of the free and open source anti-spam solution available. At the time of this writing, the version released is 2.6.1 and has a plethora of features, which is a good study by itself.
Check out the website http://www.thockar.com/assp-home/ for a detailed list of features. However, the configuration and installation of ASSP are often difficult. Once installed, the configuration would take time. For cPanel based web hosting, approximately 6000 hosts are using ASSP Deluxe for cPanel which is the only ASSP frontend for cPanel officially supported by Fritz Borgstedt, an ASSP developer. ASSP does all this by using as low CPU as possible, much less than any other spam solution for cPanel.
- ASSP Deluxe for cPanel supports following ASSP filters and features.
- Detailed logs on ASSP Deluxe cPanel Frontend.
- Bayesian Filters – The Bayesian filter powered by ASSP stops SPAM at the SMTP server. The Bayesian filter is adaptive to new spam and requires no operator intervention after the initial setup phase.
- Local addresses checks – If you enable this filter you permit your mail server to receive email only to existent email addresses on your accounts (forwarders included) stopping every email spam dictionary attack. The sender which sends an email to a not existent email on your account (i.e. dictionary@yourdomain.com) will receive the following error: 550 5.1.1 User unknown: dictionary@yourdomain.com.
- HELO – The HELO filter REJECTS email messages which do not validate Format of HELO.
- RBL – If you receive an email from a blacklisted IP address (listed on RBL) the email will be rejected. RBL permits to reduce your inbox SPAM by 30% or more.
- SPF – The SPF filter REJECTS email messages which do not validate Format of SPF.
- PTR – The PTR filter REJECTS email messages from senders with an invalid or missing PTR record.
- URIBL – URIBL lists domains, that appear in spam, not where they were sent from.
- BombRe – The Bomb Regular Expression filter (bombRe) is a spam blocking mechanism based on Regular Expressions. If there is a match to either of these Regular Expressions the message will be blocked (REJECTED) from delivery. May cause false positives.
- MX/A – The MX/A filter REJECTS email messages from senders without a valid MX or A record.
- Delaying – Also known as GreyListing, Delaying is a new method of blocking significant amounts of spam at the mail server level.
- Forged HELO – Checks Forged HELO.
- Penalty Box
- Antivirus
- Automatic Whitelisting
- SPAM Scoring mode
- Sender base checks
- Country check
- Antivirus integration
- SPAM reports
- High-end spam box collection
- Nospam tags
- Set SMTP connection limits (outgoing/ingoing)
- Set limits for attachment
All we are looking for is a distributed spam filtering ability, where hundreds of servers can use a single ASSP proxy and act as relay email server just as a few commercial spam filtering solutions like Halon and SpamExperts do.
