We host our email through GoDaddy which allows me to see how many emails each of our accounts send. I noticed one account having sent the maximum which seemed odd for that person. I feel like I have tracked it down to something sending emails in the background when Outlook is running. Let me say that again, the only time I see this unwanted behavior is when Outlook is running on this person's computer.
Another clue I have is that when I launch Outlook, I get an error that an incorrect domain is being used to send an email. While this error message is up, I do not get any unsolicited emails but once I click "OK" I will get more unsolicited emails until it hits anouther "incorrect domain" error. I can not find any of these emails in the Sent folder. I do not see them if I watch the Outbox.
I have run MalwareBytes scan (clean) AVG (clean) and Adwcleaner (clean now - found two things but nothing that fixed this problem) and still have the problem. I installed Thunderbird and let it run for several hours and no problems. It seems to me that the problem only occurs when Outlook is running but for the life of me, I can not find what the source of the problem is. I didn't find any suspicious programs running nor installed.
Short of stopping the use of Outlook, does anyone have any suggestions on how to get to the source of the problem?