migrated exchange online users are not receiving external emails.(gmail/yahoo)

What kind of migration did you perform, Hybrid? Have you checked the targetaddress attribute value? Also, domains should be set to Internal relay when the MX is still pointing on-prem.

If it happens for all migrated users, it might be an issue with the connector, usually a certificate related one, so check for that as well. Doing a message trace on O365 side should give you a clue.

Dear Vasil,

Thanks for the response. Yes its hybrid configuration with exchange 2013. I have reconfirmed  target address attribute value. I changed the domains to internal relay on office 365. Still migrated users unable to receive mail from external. We did not get any trace from office 365 message trace.

Below is the implemented scenario for our Exchange 2013.

We have one mail box server which has [mailbox, & CAS roles].
o      This server hosts the mailboxes for all users.
o      This server listens to the MAPI, OWA, outlook anywhere for all internal users.

We have one perimeter server destined to act as an edge server but with non-edge roles and services
o      This server hosts the CAS role for all external users
o      This server listens to SMTP, outlook anywhere, OWA, active sync and exchange web service.

Migrated users are getting external mail only when we use  user@myoffice365domain.mail.onmicrosoft.com.  
Any clue?

thanks for your response Mr Vasil. I fixed the issue. It was problem with the send connector. i recreated it. Now mail flow is fine.

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