We have had a number of calls asking about certain email addresses getting over 250 Emails in one go. This have been reported on two domains and we are looking into it.
One quick search on the net today shows that this is a current problem this week and the origin of many of these spams are from eastern block countries.
Emails come in as if the client was the sender and says they are being “Returned to Sender”
Delete and Ignore.