Effective Spam Filtering

Spam gets through no matter how hard we try. There is always some guy that manages to get around the filters to invade your mailbox. Now we're seeing the super spammer. They aren't satisfied with one email. They send dozens of variations of the same message over and over again, often on the same day.

When you've got some like this on your back there's only one thing to do: set up a custom filter to get rid of him permanently.

Effective spam filtering requires forethought. Yes, it's annoying but you've got to remember your good mail too. The trick is to find a way to get rid of only him while leaving flow the good mail alone.

Here's what you do:

1. Find two of his messages. One won't do.
2. Open the email and view the source. The source is key. Look at the part of the email above what you see. It's called the header.
3. Examine the header of both emails. Look for a combination of letters common to both emails - common to everything he sends. It can be anything as long as it's unique to him. For example my spammer had the characters us.newsgram.hp.com buried in the header of all his email. It's detective work.
4. Open your spam filtering software. Set up a filter that examines the entire header (often referred to as ANY header). Do not filter based on Sender, IP, or Domain as these things change with every email. Filter based on the entire header.
5. Add your unique character combination as the criteria
6. Add rejection as your action.

This filter reads: Examine the entire header for emails containing us.newsgram.hp.com and reject those messages.

Selecting the right criteria will get rid of spammers without affecting good mail. The idea is to find something unique that when blocked will not block anyone else.