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Are there spam filtering technologies that examine email headers?

For example; X-PHP-Origin header can contain an IP address that is on a blacklist; are there spam filters that would catch this?

I thought spam filters only checked the connecting client?

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do you have an example header? I don't think I've ever seen that specific header. Do you mean the PHP originating script header? There's an X-originating-IP header. Can you provide example? –  TheCleaner Jan 4 '13 at 18:34
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3 Answers

up vote 2 down vote accepted

Well, SpamAssassin for one.

Here's a list of the checks it performs:

http://spamassassin.apache.org/tests_3_3_x.html

The list notes the "area" of the email that are tested, e.g., body, header, etc.

Glancing through the list, it's entirely possible that SpamAssassin will not catch a blacklisted IP address used in your non-standard X-PHP-Origin header, as the header tests tend to look at specific header lines, and your referenced header probably won't be one of those.

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As far as I know most of them actually do.

This is actually a very basic way of filtering spam, looking at the header and compare the senders IP to black lists such as spamhaus's SBL list.

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I thought spam filters only checked the connecting client? –  josten Jan 4 '13 at 18:28
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Spam filters check lots of things. Headers, body content, IP reputation of sender, quantity of recipients...spam filtering is made up of many layers that, stacked together, will hopefully drop spams. –  Alex Jan 4 '13 at 18:42
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There are blacklists out there that use the mail headers to deny email.

In sendmail, there are many different tools available that you can configure for spam control as well.

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