Q. - "I have been sent a message warning me of a virus I should look out for; what should I do?"
Q. - "I have received an e-mail indicating a message I sent couldn't be delivered - I didn't send the message - why have I got the failure message?"
A. - It would be dangerous to be completely dismissive of such a message. Always be vigilent, as viruses are out there and they certainly can be very damaging to your machine and the data contained on it. However, the vast majority of the messages sent out are hoaxes. Indeed, the message you receive is in fact a kind of virus on its own, albeit a very low level one. There are many, many "chain e-mail" style messages out there, which encourage you to forward on the message to all your friends. This is basically a low level denial of service attack, designed to clog up mail systems and generally be annoying. If you receive such a message, before hitting the 'Forward' button, check out http://www.hoax-slayer.com or McAfee Antivirus, both of which have a comprehensive list of such messages, detailing the exact message text, so you can easily put your mind at rest and ensure you don't waste your time sending out unnecessary and inaccurate messages to your friends, family, colleagues or clients.
Prevention is always better than cure, so ensure your Antivirus software is up-to-date and be wary of messages from sources you are not familiar with, particularly if they have an attachment. If you receive a message with an attachment that you are unsure about, don't open it. Either ignore it or contact the sender and confirm they are sending it intentionally. Spoof messages are very common, whereby a message appears to have been sent by someone, when in fact, they will know nothing of it
A. - This is known as "spoofing". Basically, your e-mail address is in the public domain and has been used by someone to send out messages, made to look as if sent by your e-mail address. Usually this is a spam message advertising a product, service or website and will contain a link, for which the actual sender will receive a payment for, whenever someone clicks on it. You have received the 'Delivery Failure Notice' as the e-mail address the person sending the message sent to, is no longer valid and hence the mail server is attempting to return the message to the sender, which it thinks is you.
Sadly, there isn't a great deal you can do about this. Once your e-mail address is out in the public domain, it has a value and can be bought and sold by the unscrupulous for use in direct marketing and 'spamming'. Your best bet is probably to abandon the address and open a new one, if you are receiving a lot of spam messages and/or delivery failure notices. Often, you will receive a few over the course of a couple of days and then nothing for a while. It really comes down to personal preference whether you want to change address.