Feature Set:  

The features included in SpamSubtract Pro are limited; they do however include the ability to schedule auto-deletions of emails that contain ADV: or ADLT in its subject fields. It will also block emails that are contained in your blacklist.

Ease of Use:  

SpamSubtract Pro runs like a POP3 mail proxy seperate from your email client, detecting Spam messages before they enter your inbox. After viewing the quarantined messages you can release the message to your inbox, delete the message, or whitelist the user.

Ease of Installation:  

SpamSubtract is one of the few packages that will automatically detect your existing email clients without having to manually set each one up individually.

Stability:  

There were occasions when SpamSubtract Pro failed to work properly.

Customization:  

SpamSubtract Pro offers a limited amount of customization capabilities. The main area of customization is the "rules settings" where you can edit the criteria of your friends and interests, bad stranger, or nice stranger settings. In each category, you are allowed to further edit the criteria to try to fine-tune your filtering capabilities.

Spam Filtering:  

Their filters are not as precise as others we reviewed. It tends to allow more than the usual amount of Spam to enter your email inbox.

Overall, SpamSubtract Pro is an fair Spam filtering product and one of the few available that automatically incorporates your existing email address and populates your friends list with your existing contact list. If you don't mind putting extra work into setting up your filtering options, this package might work for you.