You should verify the content of the file if it's sent from unknown person before you open it. Most of the time you don't need such email, so it is advisable to delete it upon receipt.

Virus sometimes disguise itself in a file with extensions such as .txt or .jpg file (virus doesn't infect these files) but actually it is not. You should always make sure what kind of document it is by checking the file property etc and know which application you need to open that file. Ask yourself if you really need to open the file before you open it.

The number of email virus is increasing, and the sender of infected email most likely doesn't know he/she is infected. Such email virus has filename, subject or text body that is attractive and convincing enough for you to open it without doubt. You should be careful with such emails especially from someone you know.

If possible, you should avoid sending email with attachment because receiver needs to take extra time and work load to scan the file to make sure it's virus free. If you need to send an attachment file, you should always scan it beforehand and let the receiver know that you are sending such an email with an explanation of the file contents. Even with those details, receiver should always scan the file before opening it.

It is important for you to be fully aware of configuration and specific functions of your mailer. Some mailers automatically save the attachment file in a designated directory as a copy upon receiving such email. If you use this type of mailer, don't forget to delete these copies when you delete the original mail.