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O365 hybrid connector to onprem failing TLS
We're having issue with the connector to on-prem from Exchange Online If we enable the TLS it fails with the error Cannot connect to remote server [Message=451 5.7.3 STARTTLS is required to send ma...
Found that the STARTLS command availability depends on the security options combination enabled on the connector.
created a connector with just TLS enabled and worked
did you tried with rerun the hybride wizard on the server, this could solve the issue.
I will reach out to a former colleague of me at Microsoft maybe he has some ideas.