Here's some stuff that usually triggers off spam filters:
* Too many recipients: no more than 15 will be allowed.
* Too large message size: maximum is 2MB.
* Image links to remote sites
* Numeric IP in URL
* URL Redirect to Other Port (other than port 80 or 443)
* Empty Messages
* JavaScript or VBScript in HTML
* Frame or IFrame tags in HTML
* Object tags in HTML
* Embed tags in HTML
* Form tags in HTML
* Web Bugs in HTML
* Sensitive words
* Empty subject line
In addition to the words itself, some alternate spellings of the words will also be matched (junk versus j*u*n*k etc.)
The spam filter I use tends to give a score for each spam characteristic it finds, so feel free to send me an email at
owen@cutajar.net and I'll let you know what I find.
The other problem you may have is spam databases blacklisting your originating address/domain. If you've been sending unsolicited mail in the past this may be the case.