Thanks Bruce,

Being a bit dim I don't exactly understand these instructions

Where the message is from the specified account.
Reply with message & Stop processing more rules
Click on Specified Account an select your business account.
Add the message


And, yes, this is exactly what I got:

generate more spam and also can cause a continuos loop
bringing you undelivered mail messages from the Postmaster.

Waiting for a reply from my ISP & from Kaspersky too

Cheers
Ian