Protecting Exchange against Spam

The first thing to consider when implementing an anti-spam package is where to place your anti-spam service. It can be installed as a mail relay (or on your mail relay if you already have one) on a dedicated server or as part of the Firewall services. It can also be installed on your Exchange server.

Catching spam mail before it reaches your Exchange server seems like a good idea at first because it reduces the load on your servers in terms of CPU and database size. However, you would need to train your help desk personnel to fetch quarantined items from the anti-spam server. No anti-spam package can guarantee no false positives, that is e-mails you want to receive that are quarantined by the anti-spam server.

This means that every time someone will not be receiving a promised e-mail from he or she will have grounds for calling up your help desk people asking for them to look for mail items that the anti-spam package stopped.

For small and medium businesses this might not be an option. Their typically overworked IT staff will not want to be dealing with quarantined e-mails. Sometimes IT services are outsourced, further complicating this. So this leaves installing the anti-spam mechanisms on the Exchange server itself. This enables some anti-spam applications to deliver mail tagged as spam to a specified Outlook folder instead of the Inbox. This enables the users should they choose to do so to examine by themselves their e-mail in case they suspect it was wrongly tagged.

To complete this kind of solution I usually create a policy using Exchange System Manager that automatically deletes e-mail from the Junk E-mail folders of the users after seven days so that spam will not crowd the users' mailboxes forever.