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SMTP Delivery to Mailbox fails
We have an exchange 2013 server in the Org and we added an exchange 2019 server on windows 2022. We got an issue where Exchange 2013 cannot forward email to exchange 2019 mailboxes due to SMTP error...
Solved , apparently, checking the TLS configuration on 2013 and configuring the "client" portion which wasn't configured via registry
Run the Exchange Health Checker script across your 2013 server (and worth running on your 2019 server as well just to make sure). It should advise you what you need to do. Most likely this is a TLS misconfiguration (You should disable TLS 1.1 to increase security)