Emails to internal addresses fail to reach destination for domains that have external mail server.

Raul Lillepea 1 Reputation point

We have a tenant that has many internet domains set up. Some of these domains don't use Exchange for emails but use Google. When a user who has email in Exchange tries to send to a user who has email in Google, the email sometimes doesn’t go through. For some domains it seems it never goes through. The domains that have email in Google are already configured as Internal Relay in Exchange, but this didn’t solve the issue completely.

When emails fail to be delivered, Exchange message trace shows them as delivered, but they never reach Google mail server. The users don’t get a non-delivery response either.

What could be wrong in our Exchange configuration?

Microsoft Exchange Online
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  1. Kael Yao-MSFT 34,341 Reputation points Microsoft Vendor

    Hi @Raul Lillepea

    Have you created a send connector to send emails to the external Gmail recipients?

    From your description it seems to be an intermitted issue.

    Do the affected mailboxes have the exact same SMTP addresses both in Exchange Online and Gmail?

    Please post a screenshot of the complete message trace events of the delivered message.

    (Don't forget to hide your personal information)

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