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Exchange 2013 breaks after disabling TLS 1.0 - Version 15.0 (Build 1156.6)

After we disabled TLS 1.0 on the Exchange server running version 15.0 (Build 1156.6), all mail flow stopped. I know it was a known issue until early this year so I wondering if the issue has been resolved in any of the three Cumulative Updates released this year (12, 13 or 14)?

In my research I found this patch - https://support.microsoft.com/en-us/kb/3045301 - which was included in the CU8, but I see that we have CU11 installed on the server.

We are planning on installing CU14 in hopes that it resolves the issue, please let me know if anyone has any feedback on this issue or patch.

Thank you for your help.
1
Daaniyal Kalim
Asked:
Daaniyal Kalim
1 Solution
 
Mikhail SartaevSystem architectCommented:
https://blogs.technet.microsoft.com/exchange/2015/07/27/exchange-tls-ssl-best-practices/
SMTP is notably a protocol where Exchange acts as both a client and a server. Some older server implementations have been observed to incorrectly implement version negotiation.  In these cases, the remote servers terminate the connection when Exchange (acting as a client) offers a version newer than TLS 1.0.
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