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Legitimate mail ends up in the spam folder because somewhere, somehow, some spam filter thought it was spam. I'll look at why, and what to do.

Why is all your e-mail to me -- along with other "regulars"-- landing in my Spam folder?

Pardon my language, but ... d*mn spammers!

Seriously, so much effort is put into preventing their garbage from reaching our inboxes, and yet it still doesn't work. Not only that but we end up losing email we want as a side effect.

It's incredibly frustrating for both recipients and legitimate email senders.

Heck I'd use even strong words if it weren't for - you guessed it - spam filters.

With that little bit of venting out of the way, let's look at some of the things that cause email to land in the spam folder - or not be delivered at all - and some of the things you can do.

Content

Bad Words

The most obvious way that spam is identified is through its content, and most commonly the words that are used.

If an email message contains certain words - perhaps words relating to sexual content, body part enhancement, medications and the like - then it's possible that spam filters might assume those words indicate that the message is spam.

"All this waste simply because of @#!$@! spammers."

Of course that makes it difficult to use those words in a legitimate email - if you do, you run the risk of that message also being erroneously flagged as spam.

Sometimes the words that trip spam filtering aren't obvious, and there's rarely a way to find out exactly what they were - but sometimes they're there.

"Learning" What Looks Like Spam

There's another approach to content filtering called "Bayesian filtering" which uses a kind of statistical analysis to learn over time what spam looks like.

For example, if in your email program you get a message that you determine to be spam and you click on the "this is spam" button, then the body of that email is added to a kind of database of "things that look like spam". No dirty words needed, just a much more general concept of what spam looks like to you.

Now, when a new message arrives the filter uses that database of "things that look like spam" to answer the question "does this new message also look like spam?". If it does, by some kind of analysis, then it's marked as such.

So, for example, if you keep getting a request to dinner from your mother-in-law over and over again, and each time you mark it as spam, then eventually your email program will reach a point where that message from that person will trip the "yep, this looks like spam" filter, and her requests will end up in the spam folder. (Thus enabling the "sorry, Mom, I never got your email" defense. Smile)

Using the "This is Spam" button, though, sometimes does much more than just add it to a Bayesian filter.

Reputation

One of the parts of spam filtering that you have even less control over - both as user and as sender - is the reputation of the sender. On large email services like Google, Hotmail, Yahoo or even the spam filters used by ISPs before delivering email to you, a sender's reputation can often be more important than the content of the message.

And those terms - sender and reputation - can be subject to different definitions.

Reputation can mean:

  • How often email from a particular sender trips Bayesian, keyword or other types of spam filters. If a particular sender sends email that frequently would be marked as spam, then that sender's reputation would suffer.

  • How often individuals click on "This is Spam" on web-based email services. This is why you should never click on "This is Spam" unless it really is spam - clicking that will cause other people to stop getting it as well since it affects the sender's reputation overall.

Sender can mean:

  • The email address in the "From:" field of an email. (Unreliable, since it can be spoofed, and often is by spammers.)

  • The IP address of the computer sending the email. (Unreliable, since botnets routinely send from hundreds of thousands of compromised PCs owned by average consumers.)

Even though somewhat unreliable, the reputation of a sender is often a significant determining factor in server-side spam detection.

Tools Run Amok

Another scenario that I hear constantly are PC spam filtering tools gone crazy, typically as part of a security suite a tool is installed that integrates with your PC-based email program. That tool scans your email for you before you see it and adds spam filtering or augments the spam filtering already in the program.

Sometimes those tools apparently go nuts and decide that everything is spam. In the worst case, they delete all email as it arrives.

You can guess what I think of those tools.

What To Do

If you find that email is being filtered as spam when it shouldn't be - or you suspect that email is being blocked at your email service provider because of false-positive spam detection, I recommend these steps:

  • Examine the contents of your junk mail folder looking for false positives and be sure to click on the "Not Spam" button, or your email's equivalent, for every message that is not spam. This "undoes" some of the things that I talked about above, and makes it less likely, though not absolutely certain, that this kind of email will be marked as spam in the future.

  • If you're using a desktop email program, visit your email provider's web interface if they have one and do the same. I do this regularly with Google Mail.

  • Add senders to your contact list or email address book. Spam filters often use these as clues to the likelihood of something being spam - if the sender is in your address book then the message is less likely to be considered spam.

  • If your email service or program has the ability, add the sender to a "whitelist", or set up rules that allow you to say "email from this sender should never be marked as spam".

  • And of course if your "security suite" is interfering with your email, turn that portion of it off - completely.

Finally - sometimes there's nothing you can do.

Some email service providers are notorious for filtering out what they consider to be spam without notification. You don't get a chance to even tell the service how wrong they are, and the sender gets no notice that their email was never delivered.

All this waste simply because of @#!$@! spammers.

Article C4448 - September 16, 2010 « »

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Leo Leo A. Notenboom has been playing with computers since he was required to take a programming class in 1976. An 18 year career as a programmer at Microsoft soon followed. After "retiring" in 2001, Leo started Ask Leo! in 2003 as a place for answers to common computer and technical questions. More about Leo.

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2 Comments
bill
September 21, 2010 9:53 AM

Strong recommendation for using Gmail as a spam filter. They are very good at filtering out spam and learn from you what constitutes a good message.

Forward your email address to Gmail and use your email reader to get the mail from them. If you find a rare (after you have used it a while) spam that gets through to your email program, go back to Gmail and flag it as spam. Occasionally go out to Gmail and check your spam folder to look for accidental hits and correct them. These corrections are used to adjust the filter for your emails.

As a happy side effect, you solve another question that was posed. How to retrieve an old email. Since you can have around 7 gig of email, you never actually delete the messages on the Gmail server. It becomes the backup for old messages.

I wrote up a how-to for this a while back, since it's essentially what I do: How do I route my email through Gmail?
Leo
21-Sep-2010

Mike
September 21, 2010 12:40 PM

One thing you left out: If you have your own domain, but don't have your own server, then that means you use another server to host your domain. That means email from you may be filtered for no other reason than it's POSSIBLE that you're a spammer, even if you have never been one.

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