Trying to get the Exchange Inter-org tool to replicate free /busy info to an Exchange server in another Forest. This worked for about a year. Then one day, it broke. It turns out there were some routing changes on the other end. Mail stopped flowing also. The problems were fixed by doing some routing changes and mail started flowing again, but the inter-org never started up again. I am getting the dreaded Unable to initialize mapi interface error. Nothing changed on my end. I can ping the IP address of the other server.
I can telnet to port 25 and 135. I know all permissions are ok because I changed nothing. I am also replicating with another site just fine. I guess my question is besides port 25 and 135, what needs to be open for this to work?