You're a victim of what they call a "joe job", actually. I'm sure that this person never actually sent mail from your account, and that they never got into your mail server or anything. Instead, they wrote a program that just randomly scans inbound and outbound mail on servers that they infect and then randomly picks a to and from address to masquerade.

Usually this is a way to transmit viruses around as it plays on the trust that people have for other legitimate people (clearly you'd never open up a message from "virus@somewhere.com ", for example!) but sometimes I think that the people who work on these programs just send out random experiments to see if things work and/or they just configure them wrong.

I see this too. Not a day goes by that I don't see "Unable to Deliver Message" error messages in my inbox from messages that I never sent in the first place. The key question: did it have any attachments or try to get the recipient to go to a specific URL to "get a postcard" or "download a free Christmas tree picture" or similar?

At the end of the day, though, it's nothing you need worry about and it's also unfortunately nothing you can do anything about anyway. If you're a victim of a joe job, as you are, then your best bet is to just shrug and hope that they don't go wild with zillions of messages pretending to be from you!

The one thing I would do is notify your ISP that you're having this problem so they can ensure that they haven't left your mail server open (tell them to check for an "open relay", they'll know what that is) and so they know that you're not a spammer too. Again, they'll also know the phrase "joe job" if you want to explain that (or just send them a link to this page).

Hope that alleviates some anxiety you may have about this incident. As always, make sure you're running good antivirus and antispyware on all your computers too, and never use an open wifi network to access your mail or any other password-protected data.

In terms of protection software, I recommend commercial products, not freeware, because I have found over the years that their updates are faster and the code more trustworthy and reliable.

The specific apps I prefer are Symantec/Norton Antivirus and Webroot's Spy Sweeper. You can find Norton at any online shopping site (try Amazon.com or PCMall.com) and Spy Sweeper is available directly from Webroot [aff link]

Note that the latter link also gives you access to a free scan of your system, which is a good first step in this process too.

It's distressing to realize that the majority of PCs are now infected by one or more viruses or spyware programs, and that's always my first guess when there's any sort of anomalous behavior being reported. Be safe before you lose your precious data and files.

In addition, make double sure that you're completely up-to-date with the latest patches and updates to your version of Windows. You can do that by clicking on [START] then selecting "Windows Update" or, if you have the fancy new XP-style menu, go to Control Panels -> System then select the "Automatic Updates" tab and make the logical selections.

Hope that helps alleviate any stress you feel about this situation.