Changes to Spam Filtering

A side-effect of yesterday’s Internet Connectivity Issues was that our backup mail systems were subjected to a near 24 hour real world test, which they passed with flying colours.  All our Backup MXs performed exactly as intended without compromising the service availability for any of our mail customers even when running under loads of tens of thousands of messages.

What’s a Backup MX?

In the event of one of our primary mail servers going offline, all mail traffic is automatically transferred to one of our backup servers, called a Backup MX.  This switchover is seamless and is completely transparent to both the sender and the recipient.  The Backup MX will then store all incoming messages until such time that primary server is online again, at which point all messages are automatically sent to it.

All NamesAndSpace hosting accounts that include mail services automatically come with a Backup MX facility so that in the event of our the N&S mail server going offline, you don’t lose any messages.

Changes to Spam Filtering

At the peak of yesterday’s traffic,  our Backup MXs were storing in excess of 20,000 messages pending delivery.  Needless to say, the vast majority – more than 90% – of these were spam or junk mail.  In light of this, we are revising our spam filtering systems to purposefully intercept and eliminate a substantial proportion of spam messages before they reach individual e-mail accounts.

Our spam filtering systems work on a score-based.  Every message passing through our servers is subject to a series of checks, each of which is designed to test a particular aspect or property of the message for validity.  If a check fails, then the a value is added to the message’s spam score.  Once the score reaches a threshold value – the spam mark threshold – , the message is considered to be a spam or junk message.  If the score reaches a higher threshold value, then the message will automatically be deleted.

The changes we have implemented are two-fold.  Firstly, we have lowered the bar of the spam mark threshold.  This will have the effect of a higher proportion of messages being marked as being Spam.

The second change is more proactive.  One of the checks we employ is called a Blacklist Lookup where the address of the sending e-mail server for each message is checked against an online list of known spamming servers.  If the sender is a known spammer, then the message in question will now be automatically intercepted and deleted.

Since we implemented these changes last night, the amount of spam messages reaching individual mail boxes has reduced significantly.  These changes were not made solely in light of yesterday’s issues as we had been planning to introduce them in the near future.  If anything, yesterday merely served to accelerate their introduction.

False Positives

In the highly unlikely event you may believe that some valid messages are being marked as spam – otherwise known as a false positive – please contact our Support Team via http://www.acssupport.co.uk for further assistance.

As always, if you have queries regarding any product or service supported by ACS Limited, please do not hesitate to contact our Support Team via http://www.acssupport.co.uk.