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Exchange OWA website Redirection

Hi Experts,

We have two domains A and B that have a two AD trust between then. DNS and all AD functions are working fine between the two domains.

We are in the process of upgrading our exchange environment from exchange 2010 to exchange 2013 in a DAG configuration (two CAS servers and two Database servers).

The new exchange 2013 DAG servers are in the domain A.  We have successfully migrated the 2010 exchange users and mailboxes in domain A from their exchange 2010 environment.
We want to host the emails for domain B on the new exchange 2013 DAG servers in domain A.
The users in domain B will continue to use their AD credentials in domain B, nothing in AD will be changed in domain B or domain A.

Based on my understanding and some research, we need to configure a Link mail boxes between the two forests and perform a cross-forest migration between the two domains.

The end users for each domains are using their own registered domain to access their emails using OWA. For example, mail.doamainA.com/OWA and mail.domainB.com/OWA

The consultant that is doing the cross-forest migration portion of this project is saying that once we migrate the domain B exchange mailboxes to the target domain forest (domain A) the end users in domain B will have to use the URL for domain A in order to access their e-mails in OWA and on their smart phones.

We migrated some test users from domain B to domain A. I created a custom connector to allow emails that are sent to the migrated users from domain B to domain A to work.
However, when the migrated users from domain B tries to use the OWA URL for domain B, it does not work. I am getting the attached error message.

If I use the OWA URL for domain A for the migrated users from domain B it works.

My issue, is domain B need to keep their registered public domain to access their OWA   URL not domain A OWA URL.
IS the above possible, or I need to now tell the users in domain B that will have to use Domain A OWA URL (mail.domainA.com/OWA) to access their emails instead of their own registered domain (mail.doaminB.com/OWA.

Let me know if you need more information, I tried to explain as much as I could.
Web DevelopmentExchange* OWADNSMicrosoft IIS Web Server

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Last Comment

8/22/2022 - Mon

do you have any mailboxes / email servers in domain B?

if yes whatever migration team said is correct

Else you can do redirection with IIS redirect, however certificate must contains entries for both domains

I don't know why you are creating linked mailbox
are you creating linked mailbox 1st for all users in domain B and then gradually migrate them to domain A?


Thank you for responding.

Yes, we have a 2010 exchange environment in domain B. We want o get rid of the exchange server environment in the domain B and migrate the users mailboxes to the new 2013 exchange environment configured in a DAG. So the new exchange 2013 environment will host the user mailboxes for both domains (A and B).

We are creating link mailboxes because the users in domain b will retain their AD credentials.  we are not consolidating the AD environment, just the exchange environment so both domains can share the same GAL, calendars, contacts etc.

We would like to keep the two separate OWA URL for auto-discover for example, mail.domain_A/OWA and mail.domain_B/OWA.

I hope this information helps.


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Thanks for your reply.

I notice that if I migrated the end users from domain B as a mail enabled User, once that end users mailbox is migrated, we had to re-enable these users on the domain A exchange because the migration process automatically disabled these accounts once they are moved.  The work around that I found is to migrate the users as a linked mailbox and the migration process did not disabled these tests users that we migrated from domain B to domain A.

 I was thinking about the impact that the SAN certs would play in this process, since Domain A SAN cert does not have an entry for Domain B public domain. Also, I not sure how auto discover would work for active sync on the smart phones without a proper cert with the domains.

I guess I need to do some more testing to see what will happen.
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William Peck

you only having two owa urls for two domains
however once mailbox migrated, user will use domain A autodiscover only because his email address remain with domain A only

How you are migrating users from domain B to A, with preparemoverequest.ps1 exchange script right?
If I am recollecting correctly, the script  by default keep target accounts disabled when you migrate with preparemoverequest
Later on you need to enable that account and once you migrate mailbox, target got converted into mailbox and source get converted into mail enabled user
I feel the approach I suggested in last comment would be the appropriate


OK, Thank you for this insight.  I will tackle this beast over the weekend and let you know the results.

Thank you for your assistance with this item, I appreciate it.
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