dial-in session disconnected while sending large file

[Andika Triwidada <andika@piksi.itb.ac.id>]

Hello,

My machine acted strangely: dial-in users got disconnected while
sending large-sized emails. Troubleshooting is rather difficult, for I do
not have physical access to the server nor capability to test dialin 
connection myself. (The server is in the other side of Pacific).

A quick info on the system:
Intel CPU, Potato, kernel-2.2.17 (recompiled to support SMP),
Cyclades multiport serial card, ppp as module, mgetty.

Could you tell me how to start troubleshoot?
Maybe ppp configuration should be modified?

TIA,

-- andika