Question about Outlook Express

I keep unticking the group message box , but it keeps reverting and I have noticed all messages on a issues appear to be linked together , all to different e-mail addresses , but they should not be. I have reset passwords, gone through MacFee settings done all scans for viruses . It appears someone is able to set this so all manner of people see a message, and I keep saying no to group messages, and its compromising my position as people are able to see everything. Thanks Huronic