[OT] Someones sending spam using my Domain name !

["kw1816" <kw1816@xxxxxxxxxxx>]

For the last couple of days my inbox has been filling up with 'message
undeliverable' email bounces. All have the sender address as a random
name@ my domain name.co.uk

So I guess someone is spoofing the sender address using my domain
name, I've been into my domain control and set it to accept only vaild
addresses but is there anything else I can do ??

Thanks
Kevin W.