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

Question

_{Tuesday, January 30, 2018 12:21 AM}

I keep getting this error when trying to migrate resource mailboxes from onprem EX 2010 to O365. I have to remove all proxyaddresses, which all the domains that are listed have been added and verified in office 365. Then resync with the azure sync tool, then I have to readd all the addresses, resync , retry the move, doesn't work, repeat, delete again, resync, doesn't work, repeat. THEN maybe the mailbox will migrate after fighting with it for a while. It's so time consuming and annoying.

What causes this?

Thanks,

John Long

All replies (5)

_{Tuesday, January 30, 2018 8:15 AM ✅Answered | 1 vote}

That's the expected behavior when you have NOT added all required domains as Accepted domains in Office 365/Exchange Online. Either add/verify the domains, or continue using the workaround. You can automate it as detailed here: https://blogs.technet.microsoft.com/undocumentedfeatures/2017/02/15/troubleshooting-mailbox-migration-error-you-cant-use-the-domain-because-its-not-an-accepted-domain-for-your-organization/

Or you can license the MEU object after it has been synced to O365 and before you start the move. Assigning an ExO license will "strip" any proxy addresses associated with domains that are not added to O365. You can remove the license after migrating, if those are all room mailboxes.

_{Tuesday, January 30, 2018 9:05 AM ✅Answered | 1 vote}

Hi John,

Do you get this error first, then add and verify those domains in Office 365?

If so, I suppose that we need wait 24 hours or longer to take it effect.
Thus, please try it tomorrow or later, then check the result.

Check the namespace of your account UPN as well.

Best Regards,
Allen Wang

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_{Tuesday, January 30, 2018 3:18 PM}

Two really good replies. Thank you Vasil and Allen.

I did add the missing domains after running into this error. So it was less than 24 hours. I guess when retrying the move, it eventually hit a server that had the updated domains. I was a little impatient.

It used to be click and wait 20 minutes or whatever, now with the cloud everything is click and wait 24 hours. lol. :(

Thanks again.

_{Wednesday, January 31, 2018 2:41 AM}

You're welcome.
If there is anything else we can do for you, please feel free to post in the forum.

Best Regards,
Allen Wang
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_{Friday, June 19, 2020 10:41 PM}

I just ran into the same problem and for all those who do not work the proposed answers I tell you the reason why this failure occurred in my infrastructure

the mailbox I was moving had additional SMTP addresses to those of the domain I had synchronized with Office365.

Long story told quickly, when I validated the certificate it asked me to add associated addresses like [email protected] and [email protected]

and those 2 "domains" were not in the configuration of my hybrid exchange

hope this helps someone

regards