Exchange server dialling up ISP.

I have a clients Exchange server set to dial up the ISp to collect emails every 4 hours. The Event logs are showing that the server is actually dialling up far more frequently than this. The event logs are also showing ‘A new tcp/ip smtp connection has been received from f138.law9.hotmail.com’. This is not the connection that should be made to the ISP. Can anyone shed some light onto why the Exchange server is overriding the dial up settings and why the server is receiving incoming connections from servers and IP addresses that do not belong to the ISP.