Recently, someone on the Internet with a dislike for America Online began sending messages with an attached file called ' AOL4FREE.COM '. Think of attachments as being like a package. If you know the sender is trustworthy, the package is well labeled, and you were expecting it, the package is probably safe to open. If you don't know why you received it, the package has no label to indicate its origin, and you don't even know why you got it, you should use caution before opening it up. The likelihood of receiving a package with a bomb in it is very low, but not impossible.
Caution is always a good policy.
You know the source to be reliable and safe. If your virus software is more than six months old and has not been updated, your computer may be vulnerable. If you never open or run an attached file, it is highly unlikely you'll get a virus. Never send others an attachment unless they request it and make sure you scan a file before you send it to other people. If you're running Eudora, you can set it up to delete attachments when you empty the Trash mailbox.