Bugfix in the content matching regular expression: parenthesis were misplaced.

Adjust regular expressions:

        ... For security reasons we do not accept messages containing images 
        ... Blocked by policy: blacklisted URL in mail
        ... URL in message blacklisted
        ... MSN/Hotmail changed their blacklist error message

Bugfix: don't complain about empty callbacks.

Bugfix: make the debug flag work.

Adjust content and recipient rejection regular expressions.

Notice hotmail bounces.

Major bug fixed: parameters weren't passed through. The module didn't work. Now it does.

Search for the string "Spam source" as an indication of a problem.