I don't think Thunderbird has an opinion on viruses. Are you sure there isn't something else responsible for the warnings you're seeing?

Zenos, Then why does Thunderbird tell me that it can't write to disk? It takes the email off the server but does not load it to my computer.

The message was more like "there was a problem loading" this message". the message may contain a virus would you like Thunderbird to skip this message?" If I said no it would tell me it "could not write to disk - disk may be full, check and make sure you have permission to write to disk."

I have not changed any settings on any of the software on this computer. Thunderbird worked fine for several days then started this today. Other email programs (Outlook and the server) are not experiencing this problem.

Bottom line Zenos is YES, I am sure.