I run Outlook 2010 on my home PC. This is the only mail client I use from home. If I need to check my home email from work or a friend/relative's house, I will sometimes use the Yahoo mail service - clicking the Mail link on xtra.co.nz (nz.yahoo.com), but that's pretty rare.
Friends are advising me that immediately after sending an email to my xtra.co.nz address, they are occasionally getting a piece of junk mail, supposedly sent by my address, telling them how happy I am with the iPad I just bought. I regularly run a range of scans over my PC, which have detected nothing. I have no record of these junk emails on my PC or Sent Items Outlook folder, etc. but have seen a couple in the Sent folder on Yahoo!Xtra mail. This makes me think that perhaps my Yahoo!Xtra mail has been hacked, and the spam is being sent from my account on the Yahoo server, not my from my PC. I have therefore changed my account password, a couple of times, but the spam is still being sent.
I have contacted Telecom and Yahoo, who have both shown no interest whatsoever. Can anyone here advise what I can do to track down where these emails originate from, and get rid of them once and for all?