A topic which is often discussed is the prevention of incoming spam but what about outgoing spam from shared web servers? The standard approach is a reactive one: the system administrator will respond to an abnormally high mail queue upon detection regarding a particular server and hopefully disable the outbreak of spam. There is also always the risk that the primary cause was not properly identified and the spam activity continues, thereby repeating a further cycle of the problem.

The biggest weakness endured by this approach is that the affected server could potentially have been blacklisted by one or more Real Time Blackhole Lists and this can severely hamper legitimate e – mail deliverability for other users on the server who share the same IP Address. Once listed, it can take hours or in some cases even days to become delisted.

The alternative method to stopping the spam would be to employ a spam filter such as SpamAssassin but for outgoing messages. If you would like to have such a setup on your cPanel based server, then it is very easy to implement as per the following reference.

All outgoing e – mail messages will be scanned for spam – like characteristics and discarded if they reach the configured determining threshold value. Any existing monitoring system check will also need to be changed to rather take into consideration that the e – mail queue size is no longer important, but rather the total number of instances determined as outgoing spam by the server’s mail logs.

There will be an increase in terms of resource usage / processing but the tradeoff in terms of maintaining good e – mail reputation should be well worth the resource penalty.