DO NOT DOWNGRADE TO A PRE-MAPI BUILD! IF YOU DO, WE WILL NOT BE ABLE TO SUPPORT YOUR SERVER MOVING FORWARD! WE MADE THIS CLEAR DURING THE BETA AND iT'S WHY WE WANTED EVERYONE TO INSTALL ON TEST MACHINES BEFORE INSTALLING THE PRODUCTION BETA!
Every file on the server except .GRP files has changed and pre-MAPI versions will not know how to load or re-write files which will result in EXCEPTIONS, MISSING EMAILS and unknown behavior. Mail clients will not properly sync because clients are EXTREMELY dependent on sync keys and sync states, and everything will be lost.
A server that has been downgraded might look like its running for a short-while but that is because things are in memory. Every time the service is stopped and started more and more data could be lost.
We are releasing BETA's weekly (if not same day) if there are server wide breaking issues. Developers have been very responsive in the community while requesting more information in private messages.
Just as a modified vehicle won't be warrantied, we can't help customers that don't follow our instructions. There is no way to recover your files if you do this.