Foreign Country Block
Email-filtering companies say foreign-language spam has risen sharply in the U.S. in the past year. Symantec estimates that 10% of the 200 million spam messages its software catches each day are in a foreign language, up from about 5% just two years ago. Sophos Plc, a privately held U.K. rival, says Japanese spam has grown tenfold since January. Postini Inc., of San Carlos, Calif., says its software blocks about 20 million messages a day in Chinese.


Spam Authority
There are many companies that try to be the authority on spam. A few examples are http://www.spamhaus.org/ or spamcop.com. The problem with companies trying to be the authority on spam is clear in the following example:

John Doe has a mailing list in which people sign up for his monthly newsletter when they register, the mail comes from list@abc.com. When people sign up for the mailing list they do not let the authority they are using to protect their mailbox from spam know this. The next time Michael sends out an email he gets marked as Spam from spamcop.com even though his list is an opt-in list. The way spamcop works is, if you send a message to a person Spamcop sends you a message back saying "your not on my white list please confirm you are human then we will send your message." Michael is not checking the mailbox for list@abc.com and never responds to spamcops request, so he gets marked as spam. This could have been avoided one of two ways. The person signing up for the newsletter needs to add list@abc.com to the white list with spamcop. Michael also needs to monitor the mailbox list@abc.com and respond to request for verification from authorities such as spamcop when it was received. If you are sending out mass emails and they are legit, then you should monitor the mailbox they are being sent from for NDR (bad email addresses) and Spam Authority requests such as the one sent by SpamCop in this example.

Spam Filter Program Example - Spamalizer
Here is how a typical Spam filter program works. It scans every email and assigns some grade to it.

 
An email can get from 0 to 10 points.

Emails assigned 0 - 3.5 points are being delivered to your mailboxes without
any changes, they are not spam.

Emails receiving up to 6 points are marked as [SPAM] and will be delivered into
your mailbox as well. They are PROBABLY spam. If you want you can configure your local mail client to move them into a separate folder automatically.

Emails receiving up to 7 points are moved to a quarantine mailbox on the spamalizer server and it sends a notification to you with a link to the blocked message. You can log in by using the link to spamalizer and check the message blocked.

And emails receiving more then 7 points are definitely spam and they are deleted
automatically. 7 points is a very high value, we tested the system on many thousands emails and it didn't delete any non-spam message.
 

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