If your Yahoo email account is sending spam, this is one way to fix it
Lately, I've noticed loads of emails from friends who use Yahoo mail with no content in the body of the email except a simple link to God only knows where (I won't click it to find out). This link is sent to everyone on their email contact list (shown in the To instead of CC or BCC fields). At first glance, it's obvious that the email is pure spam to the nth degree. And while most of the time, this type of email ends up in my spam folder, every so often it will fall in line with my normal emails just because the sender's email address has been OK'd through my spam filter. Therein lays the problem and the danger.
And then, one day, this same type of spam email shows up in my inbox from ME – utilizing my Yahoo mail account to do so. I went on a search hunt through Google but found nothing to explain how to fix it. Instead of writing a WTF note to Yahoo to let off steam, I logged in to my Yahoo email account to see if I could fix it myself. After spending some time poking around the new email interface, I've come up with these steps to get your infiltrated Yahoo email box back in shape:
1. Log on to your email account on Yahoo (mail.yahoo.com).
2. On the far right you'll see some blue links (if you're on the updated Yahoo mail system. If not, just look for Options link). Click on Options, then click on More Options.
3. On the left sidebar click on Signature – if you see a creepy message in the signature box that you did not authorize, erase it. You can place your own signature there or leave it blank. Once you clear out the bad message click in the circle for the option Do not use a signature if you just want it blank. Otherwise, save your new signature, but you may need to check it on occasion to make sure the spammers do not return.
4. We're not done yet, though. Click on Vacation Response – If you see a message in either Generic or Special Response erase it and then uncheck the box for "Enable auto-response during your vacation".
5. Make sure to click Save Changes when you're done.
6. This last step is optional. If you don't really care that you have contacts in Yahoo or not, delete your contacts. By deleting the contacts you have stored in your account there will be no more spam messages going out just in case the spammers return and hijack your email options again.
7. Lastly, change your password.
If these steps don't stop the problem, you'll need to completely sweep your computer for any virus or what have you that could've snuggled itself into a folder on your hard drive. Run a good spyware program, adware, etc., just to make sure you computer is clean. I would do that anyway even if you fixed the problem with the above steps. One of the reasons the spammers use the vacation box is this – imagine all the usual spam you get on a daily basis. If you have a vacation response turned on, those spammers and advertisers are now aware of your email address and you "exist" so you'll definitely want to give your computer a good scrubbing just in case.
Outside of that, you can try to contact Yahoo. Good luck with that. 
Hotmail, Microsoft's free online email program, turned off their automated vacation response until they can find a fix since spammers were taking advantage of it as well. As of this writing, though, I could not find any information from Yahoo about this issue or if they were planning to follow suit and turn off the vacation response. So, if anyone reading this finds anything about Yahoo working on this issue please let me know in the comments below.
