I have a client who is receiving bulk email bounces "mailer-daemon" or "undeliverable" etc Today he received 4000+ His is the only one within the company that is receiving these emails. The emails state that they were sent from (for example) email@example.com which does not exist or is no such employee. All the emails are going to different companies around the world and all come back to his email acount (for example) firstname.lastname@example.org. Steps taken so far:
1. Aggressive virus scanning completed - no virues etc found
2. Aggressive spyware scan - none found
3. Reformated workstation - problem still there.
Any advise would be appreciated on what is happening and what can be done. Client is very unhappy and I need some answers to explain the issue in more detail so that they understand, and if the there is a possible solution. I have tried everything I know to resolve this issue, but I now need help. Client is now suggesting going to someone else for help if I can not resolve this.