How to detect pop3gate open

I am running an NT server that has the following specs.
NT 4.0
Exchange Server 5.5
SCSI drives hooked to an ISDN line for internet access through proxy
the exchange server distributes our email and provides connections to the internet through our upline ISP

My only problem with this configuration is that at times the ISDN connection drops. I have been 3 months troubleshooting why this drops. To no avail I have narrowed it to the telco however of course they will not take responsibility.

When this connection drops it hangs the pop3gate I am looking for a way to detect this and auto stop the pop3gate when there is no connection to the isp. Any Suggestions ?