I can't clear an SMTP address off a few accounts.

Question

Background, we migrated our tenant from O365 retail to O365 GCC about 2 years ago. The previous tenant was company.mail.onmicrosoft.com and the new gcc tenant domain was companyinc.mail.onmicrosoft.com.

We're migrating the mailboxes and all but 4 we're successful.

Error: NotAcceptedDomainException: You can't use the domain company.mail.onmicrosoft.com because it's not an accepted domain for your organization.

Should be a simple fix. Remove the SMTP address and resync.

Removing the SMTP address from EAC I'm able to click the minus to delete and the domain, click save and the page closes. Reopen the properties page for that user and the address is still there.

Attempt #2..Exchange Mgmt Shell

Set-Mailbox "Purchasing" -EmailAddresses @{remove="smtp:purchasing@company.mail.onmicrosoft.com"}

Command seems to run successfully however running "get-mailbox -Identity purchasing | Format-List *" shows the SMTP address is still there.

As an alternate, Microsoft recommends setting the smtp address and omitting the unwanted address.

https://learn.microsoft.com/en-us/exchange/recipients/user-mailboxes/email-addresses?view=exchserver-2016

Again, the command seems to run successfully but the SMTP address remains on the mailbox.

Interestingly. I attempted to edit the SMTP address purchasing1@companyinc.mail.onmicrosoft.com. It just adds an SMTP address, leaving the original untouched. I can also delete the newly created record without issue.

Answer 1

Hi, @Root777

Great to know that the issue has already been resolved and thanks for sharing the solution so that others experiencing the same thing can easily reference this!

Since the Microsoft Q&A community has a policy that "[The question author cannot accept their own answer. They can only accept answers by others Accept answers on Microsoft Q&A | Microsoft Learn]", I'll repost your solution in case you'd like to "[Accept ]" the answer : )  Accept answers on Microsoft Q&A | Microsoft Learn   

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Issue Symptom: 

Fail to clear an SMTP address of a few accounts.

Error: NotAcceptedDomainException: You can't use the domain because it's not an accepted domain for your organization.

Resolution: 

Modify the Email Address Policy under mail flow in EAC.

Answer 2

Well if you've found yourself in my shoes the answer was to modify the Email Address Policy under Mailflow in EAC.

I removed the alias@company.mail.onmicrosoft.com from the policy and I'm able to delete the unwanted SMTP record.