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The current environment is in Hybrid mode, where we are in the process of migrating user mailboxes from On-prem Exchange 2010 to O365. The issue is reported only for O365 mailboxes, not for On-prem users. We migrated few mailboxes to O365 and O365 mailbox users can send/receive emails normally to external recipients with the default domain(xyz.com); however, OOF replies to external addresses drive out with the default Microsoft domain(xyz.mail.onmicrosoft.com) instead of the default domain, i.e., xyz.com.
We don't see this issue for Internal OOS replies and affects only to external senders. All Mailboxes have an email Alias set up along with the default domain. Target email address in ADSI edit is set to xyz.mail.onmicrosoft.com.
Can you please assist with this?
Regards,
Kannan
Hi David, Yes, we enabled the Centralized mail transport in Hybrid config and don't have the On-prem server to manage the synced mailboxes.
Hi, Did the external users receive the external OOF or internal OOF? Is there any 3<sup>rd</sup> party mail filter software in your organization? How did you configure remote domain? Please provide the result of get-remotedomain. You also need to get message tracking log to check if there are any other rules/agent change the mail flow.
I suspect with the centralized routing, the OOFs are going out through on-prem and picking up the remote routing addresses for the accounts rather than the default reply address. ( which I assume is set to the custom domain correctly)
have you enabled Centralized mail transport in hybrid? Sounds also like you do not have an Exchange Server on-prem for mgmt of the synced mailboxes? Also, take a look at this thread: https://www.reddit.com/r/msp/comments/zyav8r/365_mail_accounts_defaulting_to_onmicrosoftcom_as/
Yes, I reviewed the article already and created the connector as described in the article, but it didn't help to resolve the issue.
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Same issue here. Hybrid Exchange environment, with a mix of on-premises and EXO mailboxes. Routes set up with connector so that every mail is sent through our on-premises infrastructure. When OOF is enabled on a migrated mailbox, it is sent via its mail.onmicrosoft.com address, although primary address is ourdomain.com.
Any clue?