Exchange 2013 Server delivery model for non-exclusive domain

I am trying to figure out if there is a way to set up an Exchange server with the following criteria:

Background - our company is changing names and adding global partners.

Many addresses @domainA.com will be local users that connect to their existing mailboxes on the server.

Other addresses @domainA.com will be users who are running other mail services (not necessarily Exchange servers) located remotely in other parts of the world. These may be their own mail servers or a service provider like an ISP or Google Business Apps.

Internal and External email should be delivered to the local users where appropriate, but should be forwarded to the destination mail server for delivery for those users who are not members of the local domain.

Everyone should be able to send and receive from their @domainA.com address.

Is it possible to run this kind of set-up, and if so, what features or setup do I need to research?

Thank you in advance.

Christopher BeaugrandCIOAsked: 2014-03-03

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LVL 63

Simon Butler (Sembee)ConsultantCommented: 2014-03-03

It is possible to run this kind of setup, but it is going to be a completely nightmare to setup.

You can only have one set of MX records, which means your server would have to be responsible for delivery of all the other sites. Then to route the email to the correct server you would need to have contacts and dummy domains all over the place.

The option I have seen most common for this scenario is sub domains.
So you would have @ location.example.com
That would allow you to have separate MX records for each office and it doesn't matter where they host it.

Another option would be to use a cloud service that can do location based routing, again it will require some degree of manual work to maintain.

It is going to be almost impossible to have anything automatic.

Simon.

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Christopher BeaugrandCIOAuthor Commented: 2014-03-03

Thank you Simon. I had considered subdomains and may go that route if there is no other viable option.

LVL 63

Simon Butler (Sembee)ConsultantCommented: 2014-03-04

The other options are viable, but it will require a lot of work. Every new user created by any site would need to be created in the domain somewhere, either on Exchange or a hosted platform, so the emails are routed correctly.
Then you would have to ensure that every server being used is in the SPF records and the other providers are setup correct for your domain. You will in effect lose control of your domain.
One of the other sites does a mailing list with a dodgy return address - it comes back to your service and your reputation.

Simon.