Double emails

[Malcolm McCallum]

Hi everyone, I am using Mail in Mac OS X and I am on cable. I have a ISP 
(highway1) and of course Telstra Bigpond. I access Highway1 through 
Cable and get double copies of all emails which is a bit of a pain :-( . 
Can anyone tell me where I am likely going wrong.
Mac
Malcolm J McCallum
16 Alyth Road
Floreat
Perth 6014