And whats wrong with Microsoft software?

There are some viruses as SVPII pointed out that can execute upon opening a mail but most still sit as an embeeded part of an attachment. If you are using Outlook, by default it will warn you before opening any attachment that could possibly contain a virus.

Good suggestion though, put FT or the likes in the subject field, most of the people that send mails to me do.

Thanks,
Richard