Using same alias for Shared Mailbox in multiple domain

Exchange

Scenario

Alias is a key parameter of a shared mailbox to make it unique in the backend, especially if there are multiple domains.

An example of this is when two domains (domain A and domain B) want to create a shared mailbox for their respective IT teams. To mask the address name “it” with an alias, the system needs to know that the two “it” mailboxes are unique from their respective domain. In this example, the IT mailbox for Domain A will have an alias of “ita” and the IT mailbox for Domain B will have an alias of “itb”.

Setup for domain A exo-config-same-alias-multi-domain-a

Setup for domain B exo-config-same-alias-multi-domain-b

Steps

Use the Classic EAC to update an alias

You can access Exchange Admin Center (Classic)> Left Pane> Recipients > Shared\Mailbox > Click the target mailbox > general > click more option to make the alias field available.

References