Hybrid mail flow issue: Outbound emails from on-premises mailbox to office 365 users is not working

Benard Mwanza 996 Reputation points
2021-11-25T17:27:08.863+00:00

We have currently renewed exchange server certificate, and assigned IIS, SMTP, IMAP services. Afterwards, on testing mail flow, we noticed that emails send from on-premises mailbox cannot reach office 365 mailbox or user. Emails send from office 365 can reach on-premises mailbox.

Services from odd certificates cannot be unassigned its greyed out.

What can we do to resolve this?

Microsoft Exchange Online Management
Microsoft Exchange Online Management
Microsoft Exchange Online: A Microsoft email and calendaring hosted service.Management: The act or process of organizing, handling, directing or controlling something.
4,058 questions
Exchange Server Management
Exchange Server Management
Exchange Server: A family of Microsoft client/server messaging and collaboration software.Management: The act or process of organizing, handling, directing or controlling something.
7,227 questions
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2 answers

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  1. Andy David - MVP 138.6K Reputation points MVP
    2021-11-25T17:33:36.137+00:00

    Did you re-run the Hybrid Wizard after renewing the cert and associated mail flow with the new cert?


  2. Andy David - MVP 138.6K Reputation points MVP
    2021-11-25T19:06:33.22+00:00

    If you dont want to re-run it then ensure the new cert has the correct subject and issuer and that is set for the send connector:

    $NewCert = Get-ExchangeCertificate -Thumbprint <thumbprint>
    $TLSCert = (‘<I>’+$cert.issuer+'<S>’+$cert.subject)
    Set-SendConnector -Identity “Hybrid Send Connector” -TLSCertificateName $TLSCert
    

    If it still doesnt work, what is the NDR you get when sending or the error in the queues?