Routing intra-granization Exchange emails to Lotus Notes through VPN

[DOSA]

Hello. I need to route all emails from our company to our parent company through the IPSEC VPN tunnel between the two companies. We want to send/receive emails between the two companies through the VPN and NOT through the Internet. Our company is running Exchange 2003 and our parent company is running Lotus Notes. I have 2 questions.

1. From Exchange 2003, how do I route all of our emails through the VPN tunnel to their Lotus Notes server?

2. I need to put in an alert system that will alert us in the event that our emails are not getting delivered to the Lotus Notes server. Any suggestions on how I can set this up?

Thanks in advance for your assistance!