Yahoo Messenger
"I doubt this has much to do with installing Yahoo Messenger, unless you've removed it and realised the speed improvement?"
If anyone's interested I have discovered that it was the Yahoo messenger which was capturing emails sent from my btconnect server to any yahoo addresses and then sending them 48 hours later. I know now because I have deleted the messenger!
I imagine yahoo may do this to stop people using a fixed ISP and forwarding all messages to a yahoo account...
Bill