Dialup when checking mail when it shouldn't

[Richard]

I have a client that has an e-mail account that everytime
he is on the local network it tries to dial-up to check
his e-mail. I have checked the areas of connection and
made the program either ask before moving to that
connection style or not connect at all through a modem.
He is still getting this error. Can anyone point me in a
different area other than Internet connectivity or Mail
connectivity that could be causing this?

Thanks

Richard