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Use same alias for Shared Mailbox in multiple domain

May 23, 2018 | by iaur | posted as Administration, Exchange Online


  • You have multiple domain in one M365 tenant
  • You want to organize your shared mailboxes with respect to their functions (i.e. and


To utilize the same alias for Shared Mailbox in multiple domain, Access Exchange Admin center (classic) > Left Pane> Recipients > Shared\Mailbox > click more option to make the alias field available.

Alias is the key parameter of a shared mailbox to make it unique in the backend specially if you have multiple domain.

For instance, I have two domains (domain A and domain B) and want to create a shared mailbox for both respective IT teams. Hence, and

By design, the address name “it” will be unique address in the entire tenancy. Therefore, you need to mask it with an alias for the system to know the two “it” mailbox is unique from their respective domain and so that the creation will push through.

In conclusion, the IT mailbox for my Domain A will have an alias of “itA” and Domain B will have an alias of “itB”.

(Please see screenshot for more information)

Use same alias for Shared Mailbox in multiple domain
New Shared Mailbox - Google Chrome 
new shared mailbox 
Shared mailboxes allow a group Of users to view and send 
email from a common mailbox and share a common 
calendar. Learn more 
*Display name: 
IT @ Domaina 
•Email address: 
The following users have permission to view and send mail 
from this shared mailbox. 
The user's alias is the 
portion of the email 
address on the left side of 
the @ symbol. It must be 
unique in your 

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