Azure AD Connect (Support Assistant) reports .com domain is non-routable

We are running the Microsoft Office 365 Support Assistant before setting up the Azure AD Connect tool for directory sync, but the domain verification (step 2) reports that our .com is non-routable and this type of domain is not supported.

The domain is already verified in Office 365 and has no problems. Our internal domain is the same as our external domain ( and we only have a single UPN ( We are using our own DNS and have not added the Office 365 DNS entries (reported DNS errors are ignored in the portal). We are not using a sub-domain.

Does anyone know why the domain verification step is reporting that our .com is non-routable?

LVL 15
Lee OsborneSenior Infrastructure EngineerAsked:
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Hasin Ahmed ChoudharyExchange AdministratorCommented:
Is it showing for your default domain?

Follow this:

I think you can select correct domain while starting the first sync.Also, check if any mailbox has any other accepted domain?
Lee OsborneSenior Infrastructure EngineerAuthor Commented:
Thanks, Hasin. Our .com is showing as the default domain. We're running a Hybrid model with Exchange 2013 on-premise and not cutting over the domain, and we haven't got as far as actually running the AD Connect tool yet as it's the Microsoft Office 365 Support Assistant which reports the .com is non-routable.
Vasil Michev (MVP)Commented:
Just ignore this. The tool has not been updated in ages and it doesnt account for every possible configuration anyway.

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Lee OsborneSenior Infrastructure EngineerAuthor Commented:
Vasil, thanks. That's the route we were probably going to take, but good to know it wasn't something potentially wrong!
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