This is what our hosting service Hostgator had to say…
“After investigating, we found that the user ‘******’ contained a malicious file that had been evading detection by our automated tools and therefore remained on the account able to send out spam emails. At this time I have gone ahead and manually deleted the following malicious file:
/home/*****/public_html/wp-content/cache.bk/supercache/………………………………………………………………/ajax72.php
Currently we are going through and removing the remaining spam emails in the server’s mail queue. Please standby…..”
Please notify if you have any solutions.
Thanks