We are having a problem with multiple companies not being able to reach any of our clients by e-mail.
We have an Exchange 2010 server with latest updates.
When an e-mail is sent the external users gets the error:
403 4.7.0 TLS handshake failed.
I have tried disabling TLS and enabling basic authentication on the receive connectors but that didn't help either.
I have checked the certificates and they are still valid.
I have used http://www.checktls.com/index.html
to see if TLS works and it does.
I have tested incoming SMTP traffic with https://testconnectivity.microsoft.com
and that doesn't give any errors either?
Please advise on more steps I can do to find the cause of this problem.