I use Outlook 2007 and it appears to be sending e-mails to lots of people that I know nothing about. Initially, I received a few e-mails back from other peoples spam filters but recently I have been receiving numerous (over 500 a day) "bounce back" messages from my mail administrator because messages have been undeliverable.
My Anti-Virus software (Bitdefender) can't find any virus.
What should I do? I have temporarily set up a rule to delete the bounce backs.