I'm in the process of building an exchange 2013 environment,  the mailbox server will be located on our internal network and the edge server in the DMZ.  My question is does edge server that's located in the DMZ need to be on the domain?

I'm in the process of building an exchange 2013 environment,  the mailbox server will be located on our internal network and the edge server in the DMZ.  My question is does edge server that's located in the DMZ need to be on the domain?

No. THe Edge is designed to be in a DMZ. You sync it with Mailbox servers that are in the domain

https://technet.microsoft.com/en-us/library/Aa997438(v=EXCHG.150).aspx

Hi,

the edge server may never be in the AD domain, just create a dns record in the domain that points to the edge server.

how to install exchange 2013 edge server :

http://exchangeserverpro.com/installing-exchange-server-2013-edge-transport-server/

Hi,

the edge server may never be in the AD domain, just create a dns record in the domain that points to the edge server.

how to install exchange 2013 edge server :

http://exchangeserverpro.com/installing-exchange-server-2013-edge-transport-server/

It can be in a domain actually if you want.