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Exchange 2016 server not sending or receiving emails

If the server is up and running but users cannot send or receive any email, follow the steps:




Get the last error:

Get-queue | fl

Look for “LastError” in the results.





If you are getting error:

[{LED=451 4.4.395 Target host responded with error. -> 451 5.7.3 Cannot achieve Exchange Server authentication};{MSG=};


Means that maybe the authenticated certificate is not installed or somehow corrupted





Look for “CN=Microsoft Exchange Server Auth Certificate”.

Copy its “Thumbprint”


Enable-ExchangeCertificate -Services SMTP

And paste the “Thumbprint”



The server should be up and running in few mins after.