I received about 8 emails from firstname.lastname@example.org saying it is an automatically generated delivery status notification stating that delivery to the following recipients failed. When I look at the recipients listed I have no idea who any of them are. Most seem to be French and some of the emails are in that language. I have also received a few emails from addresses I deal with saying there is irregular activity on my account. Comcast also would not let me sign in to my email until I reset my password. Any suggestions?
Check your Sent folder to see if anything is in there that you know you didn't send. If there is, then the account has been compromised. In that case you need to change the password to something a lot stronger than whatever it is right now, and also change the secret question and answer for the account.
If the Sent folder looks OK, then the most likely thing is that your account is being "spoofed". Spammers can make it look like emails came from you when in fact they did not. If that is the case, there is nothing you can do except notify your contacts of the problem and wait it out. Once a spammer has your email address there is nothing you can do to stop it. But in order to avoid detection they will usually only use an address for a few days or a week and move on to annoy someone else. The bounce messages are due to the fact that the spammer is sending to email addresses that are no longer valid. You should find this of interest-------------
Also, use your A/V software to run a complete scan of your machine to see if it can find anything wrong.