Outlook issue while connected to a separate VPN

Hi, 

Please can someone help me out, currently in my company we are using exchange 13 users are using win7 with outlook without any issues, we have now recently merged with a new company lets say company B so the users in my company are connecting the company B via VPN for file access and all while doing so users in my company are experiencing that after a while outlook gets disconnected while working over the vpn. 

i have tried static route on windows 7 but not having much luck. 

Please help. 

Thanks 

Juan