Mail not being delivered between Office 365 and on-premise Exchange during cut-over migration.

ajdratch
ajdratch used Ask the Experts™
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I am doing an Office 365  cut-over migration from Exchange 2010.  I moved a couple mailboxes and now user's whose mailboxes are still on Exchange 2010 cannot send to mailboxes that have been moved to Office 365.

I successfully ran the Office 365 hybrid configuration.

In office 365 I added connectors from "Your organization's email server" to Office 365 and from Office 365 to "Your organization's email server."

What do I need to do to get mail flowing between mailboxes still in Exchange 2010 and mailboxes that have been moved to Office 365?
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Richard InnesSenior Consultant

Commented:
Can you clarify whether you are doing a cutover or hybrid migration as the approach is different for each?

If hybrid, the wizard should have created a send connector to Office 365 and you should see it under send connectors. Check queue viewer on EX2010 to see if the messages are being queued.

Author

Commented:
I'm doing an express migration cutover. Once all mailboxes are on Office 365, I'll stop the syncing.
Richard InnesSenior Consultant

Commented:
Also check that you can telnet out to Exchange online protection on port 25 from your EX2010 server.  Check the MX records for the .onmicrosoft.com domain for your tenant and that's what you should do the test telnet to.
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Author

Commented:
I am using that process. I am at step five

When I look at the domain .onmicrosoft.com, the only DNS records are v=DKIM1 txt records
Richard InnesSenior Consultant

Commented:
The migrated users should have the routing address of tenantname.mail.onmicrosoft.com stamped on the targetaddress attribute on their AD user object as part of the mailbox migration.  Mail addressed to these users should then be sent via the Send connector named Outbound to Office 365.

Author

Commented:
I'm missing that send connector. Can you let me know how it should be configured? Should the MS Office 365 hybrid configuration have created that?
Senior Consultant
Commented:
It should be created when running wizard for the minimal hybrid, you can check log of hybrid here - %appdata%\Roaming\Microsoft\Exchange Hybrid Configuration.

Send connector should be scoped to Office 365 routing domain for your tenant and configured to send using MX records.

hybrid.jpg

Author

Commented:
I added the connector but still not working.
This migration uses both domaincom.onmicrosoft.com and domaincom.mail.onmicrosoft.com I'm not sure what the difference is.

The users logins on premise are three initials and their email address is full name. The user's attributes in on-premise active directory is fullname@domain.com, fullname@domaincom.mail.onmicrosoft.com  and fullname@domaincom.onmicrosoft.com.

The office 365 mailbox has fullname@domain.com, fullname@dcbflegalcom.mail.onmicrosoft.com and initials@domaincom@  domaincom.onmicrosoft.com. It does not have fullname@domaincom.onmicrosoft.com.

The bounce back when sending from an on-premise mailbox to an Office 365 mailbox shows
fullname@domaincom.mail.onmicrosoft.com
BL2NAM02FT005.mail.protection.outlook.com #550 5.4.1 Recipient address rejected: Access denied. AS(201806281) [BL2NAM02FT005.eop-nam02.prod.protection.outlook.com] ##rfc822;fullname@domain.com
Richard InnesSenior Consultant

Commented:
For the Office 365 connector "Your organization's email server" to Office 365" is the correct external IP address configured for where the mail is being sent from?

This address fullname@domaincom.mail.onmicrosoft.com is used as the mail routing address between on-premises Exchange and Office 365 so should definitely be stamped on the target mailbox.

Author

Commented:
It is working now. Adding the send connector and updating mail.onmicrosoft.com fixed it.

Thanks
Richard InnesSenior Consultant

Commented:
Good to hear it is resolved.

Cheers,
Richard

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