Question : Internet emails accounts compromised

Within a 24 hour period, there are three people who I support  on our work network whose personal email accounts have been compromised (2 yahoo and 1 aol).  All three email accounts have been sending spam messages to everyone in their contact list.  These accounts have not been spoofed as the emails are in the sent items folder.  I've run a deep scan on two of the workstations that thes users use while at work and both came back clean.  The only other piece of the puzzle is that they all use their blackberries to monitor their personal email acccounts.  Is this just a coincidence that they were compromised within 24 hours of each other or could I have a problem on our network?
Thanks,
John

Answer : Internet emails accounts compromised

I have seen this with a residential customer on AOL. Examination of the sent items folder messages showed that they were sent about 10 at a time from three machines - one in Poland, one in Greece and one in India. The client software sending the messages was the mobile version although the end user did not use any mobile device for email.

Changing the password to a strong one fixed it. No come back 6 weeks later.