getting booted

I am having a problem with getting booted from the internet the isp says it is due to an email that is over 125kb ….I don’t think so, all my internet settings seem correct could it be the modem going bad? thanks for the input…p.s. the longest the pc can stay connected is 2 minutes if I open the email it gets booted as soon as it begins to recieve mail and doesnt stay on long enough for a webpage to open