We have an issue where 2 of our users are receiving spam which is addressed from themselves. That is, for example, 'user a' receives spam which has 'user a' in the from field. I've done a spyware and antivirus scan, both have come up clean. I've come across the normal issue, where spam seems to originate from some random email address, but i've never come across it where it appears to come from a genuine user. Does anyone have any ideas on how to resolve this problem?