Spammers sometimes insert the text of a message inside invalid HTML tags, in an attempt to confuse statistical word filters. This is because the text in the invalid tag is read by the filter as non-spam words and they balance out the spam words. Some examples are shown below:
Examples
<comment>Get Rich Quick</comment>
IMail Server treats all non-standard comment formats as invalid tags.
<Get paid to work from home. Respond now for information on this fantastic offer. There are a limited number of available positions, so don’t miss out. Respond Now!>
Here, text is hidden by e-mail clients because it appears within an invalid HTML tag.
In the past, the statistical filter of IMail would not catch these as spam because it could not read any text inside HTML tags. Now the HTML parser will extract the comments from the text, so that it can be examined by statistical filtering.
If you select the Invalid Tag option in Feature Filtering, messages containing this type of spam trick will automatically be identified as spam.
Note: IMail Server considers any tag that is not HTML 4.0 compliant to be an invalid tag.