The junk filter is only going to identify known senders. If they're using multiple addresses, each one will be different. IS your Outlook junk mail filter up to date?
I also use Cloudmark's Spamnet to identify junk. Each time one of them is marked as such, a report goes back to Cloudmark and that address is updated in their database.
Another option is to use a rule if there are common words in the subject line and simply delete the message or move it to a certain folder if it meets the criteria of the rule.
Bottom line, the only way to stop junk mail is to change your email address. Yes it's a PITA but once your email address is out there, it's available to anyone.