BleepingComputer.com: adsl droped after email

Hi there i have a very confusing problem. I would be grateful for any help I can get. I have a adsl connection and check a few email boxes. Whenever i check one box even doing it independently of the others, I loose my internet connection. This happens on 2 computers on the same network. I can check the others with no problem at all. I have checked this one via web mail and noticed a fair amount of spam could this be the issue? thanks

Have you checked via web mail if there is maybe a large file?
I remember that somebody sent me a report (work related) with a very big file size, and my email program went crazy, and my connection stopped. I had to access my inbox via web mail to get this problem sorted.