No filter software and my mail software does not scan for bulk or spam.
In other words. I use the standard WikiSysop user created by the installation routine. I go to my Wiki and log in with the mentioned user. I use the preferences to set up a email address. After using the link in the confirmation mail the email address got confirmed. Then i checked the 3 boxes to get emails for changes on wiki pages, on user pages and on minor changes. So, then i change an article in my Wiki and I'm saving it. My email server does not get any mail (i've tailed the logs of postfix).
I had the same problem using
* Mediawiki 1.5.2 * PHP 5.0.5 * My SQL 5.0.15
on Windows XP SP-2. I could see that "my watch list" is showing correctly as is the "recent changes" but no sign of the e-mail (all the others are fine though). I set up dumpster (http://quintanasoft.com/dumbster/) to see what exactly was coming out.
Problem in my case came down to UserMailer.php with the line
$adminAddress = 'WikiAdmin <' . $wgEmergencyContact . '>';
Dumpster seemed happy with this but my normal SMTP server didn't like it giving me a "501 5.5.4 Invalid Address"
Changed it to
$adminAddress = $wgEmergencyContact;
and problem gone.
Hope this is of some use to you.