In my lab environment I have been setting up two exchange servers. One in the forest in which the FIM services are located, and one in another forest. I want to play around with the built-in GAL Sync functionality.
Creating the MA for the forest the FIM services were in was no problem, however once I started creating the MA for the other forest I got the following error:
“The LDAP server is unavailable”. This seemed odd as in the previous step of the wizard I was able to successfully select the desired Organizational Units. If I ignored the error I was stuck with the wizard stating "It appears this forest is not exchange enabled”.
After installing the FIM 2010 first update, the error magically went away. I’m not sure it is because of the update, but it sure does like.
The FIM updates can be downloaded and installed from windows update.
Another person suffering the same issue: serverfault topic