A customer in a Hosted Exchange environment needs to have a all of their outgoing emails routed to a Smart Host for encryption purposes. Only the email coming from the one domain on the server needs to use this connector, all others can use the default connector. Can this be done? if so, How?  

Hi!

I think you are looking for this:

https://technet.microsoft.com/nl-nl/library/jj839710%28v=exchg.141%29.aspx

Hi Matt,

You can use Exchange domain security to use this ferature

Follow this steps might help you 

http://exchangequery.com/2014/05/22/exchange-2013-domain-security/