Nick you need these 2 sites to help work out were its coming from. From the e mail look at properties, then message source to give you the details. Most of the e mail addresses are spoofed so no point in trying to reply to them. Better to aim at whoever is hosting the web site since most web hosts have anti spam policies.
Alternatively if you are using MS Express use "create a message rule" to delete anything with key words in it like "mortgage". Not difficult to do as the software helps you along.