I have started to get a load of Delivery Failure messages in my inbox which I haven't sent. They are returned to a random 4 or 5 letter usename at my domain e.g wesc@'mydomain'.co.uk and all come from different 'postmasters'.
Any ideas what/why this has suddenly started.
I run Norton - up to date virus checker and access the net via a router with firewall.
Thanks - I was worried that something had got in and was sending random mails from my m/c. Can't see how and the addresses that the failures are coming back from aren't any that I know or would send to.