Hi

I have EXchange 2013 SP1 DAG, Node Majority where 2 MBX servers in the primary site and 1 MBX server in the DR Site. If there is a simultaneous loss of the 2 MBX servers in the primary site as in a power failure, then quorum will be lost. 

How can I recover operations using the MBX Server in D

You would need to do a Data Center Switchover for moving the quorum forcibly to DR Site. 

you may refer to the links about Datacenter switchover which are enclosed below:

https://technet.microsoft.com/en-us/library/dd298067(v=exchg.150).aspx

https://technet.microsoft.com/en-us/library/dd638215(v=exchg.150).aspx

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Hi ,

Agree with Pavan.

Datacenter switchover is the only option.If there is simultaneous failure happened on all the nodes in the primary site or else an primary datacenter failure then there wouldn't be an enough time for the cluster to recalculate and adjust the quorum.So the only way is to do an datacenter switchover.

Reference link for datacenter Switchover :

http://smtpport25.wordpress.com/2010/12/10/exchange-2010-dag-local-and-site-drfailover-and-fail-back/

Above mentioned article is for exchange 2010 even though the steps defined on that article is same for exchange 2013.

Reference kink for Dynamic quorum : 

http://www.msexchange.org/articles-tutorials/exchange-server-2013/high-availability-recovery/exchange-2013-dag-dynamic-quorum-part2.html

Please reply me if anything is not