Bill,
I have found this to be true also. I can dial in on both my laptop and desktop at the same time from my home/office. Same physical location, but separate phone lines. In fact, when I am on the road, I have sent e-mail back and forth in near real time using the same account. The first time I did this, I figured there would be an error message warning me that the account was already in use, that isn't the case.
You would want to make sure your on line time is unlimited, especially if someone else is using your account.
Another interesting thing is as JoeG mentions. I can dial into a different ISP and receive my e-mail through that portal. You just have to say OK, when IE asks if you want to check for e-mail on the existing connection.
Shelby
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2001. 5 2500 QC LB 4WD, ETH (Built 09-10-00), DEE, 3. 54 gears, Laramie SLT, Camper Special, Trailer Tow, Travel Convenience Group, Power Driver Seat, Alarm System, Remote Keyless Entry, Fog Lamps, Cab Clearance Lamps, HD Transfer Case, Bright White with a Gray Interior. Built 09-15-00, took delivery on 10-06-00, 3873 miles as of 01-04-01. Custom aluminum work body / flat bed. Coming soon: E-Brake and gauges.