Most viruses are delivered through email attachments. Attachments that contain viruses are either executable programs (file types: .com, .exe, .vbs, .zip, .scr, .dll, .pif, .js) or macro viruses (file types: .doc, .dot, .xls, .xlt). The safest way to avoid them is to not open attachments.
The good news is that downloading and reading the email will not do you any harm. As long as the attachment is not opened, the virus will not open and attack your computer. If you don’t know the sender and if the email text is suspicious just delete the email along with the attachment.
If one of your contacts was infected by a virus the virus is not so easily spotted. Carefully review each email and play it safe. Many web mail services can scan email attachments for viruses. If you use a desktop mail program like outlook and don’t have a virus scanner that can scan email attachments you may save (not open!) the attachment to your hard drive where it becomes accessible for your virus scanner.
Just remember never to open an attachment before it was scanned.
Basic rule of thumb is that, if you are not expecting an attachment/e-mail from someone or don’t recognise it , simply delete it.. If it is important someone will chase it up or re-send it to you. You can always double check with the sender if unsure also.