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marktt asked joyceshen-MSFT commented

Exchange contact

If we've single domain with 2 different o365 tenants, If I create a contact card for separate o365 tenant , it can't be send out.
400 4.4.7 Message delayed' (Proxy address added
550 5.2.0 RESOLVER.ADR.MissingPrimary; recipient primary SMTP address is missing (Without SMTP:user@domain proxy address).

How can I send mail to on-prem contact card to different o365 tenant?


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Hi @marktt

Did you deploy a hybrid for your on-prem domain and o365 tanant?

Can the mail be successfully send to the external contact directly without using contact card? How did you create the contact card, have you tried creating mail contact in o365 EAC?
Manage mail contacts in Exchange Online

And the introduction about (Remote Server returned 550 5.2.0 RESOLVER.ADR.BadPrimary) error when an Exchange Online user sends mail to an external contact

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Yes, we have separate hybrid server for different O365 but share same single forest. It conflict with existing AD object.

it can be sent without using contact card.

Can we create a fake address(another O365 tenant) and route to the fake address (another o365 tenant) ?


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Hi @marktt

Are you getting the error information like this? The proxy address "" is already being used by the proxy addresses or LegacyExchangeDN of "". Please choose another proxy address.( The "UserMailbox" with display name "XXX" is already setup and using the same address.)

We could refer to the introduction in the official document: Global address lists (GALs): The built-in GAL that's automatically created by Exchange includes every mail-enabled object in the Active Directory forest.

So the users in the same single forest will be considered as internal users. They already have a recipient type and we could not add another type for them. You could check if you can see the users in GAL as well.

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