Issues with proxy server cetificate – Exchange 2016

Lately I went into an issue where users recieved a dialog box in outlook saying, there is a problem with the security certificate;

The customer is running on Exchange Server 2016 and is using a Kemp Loadbalancer.

This MS article;

https://support.microsoft.com/da-dk/help/923575/error-message-when-outlook-tries-to-connect-to-a-server-by-using-an-rp

states that there is a problem with the security channel

Finnaly I  found this article on F5 https://support.f5.com/csp/article/K10433354 and i decided to remove all normal DH Cipher suites from the Kemp Loadbalancer, so only the following suites are enabled;

ECDHE-ECDSA-AES256-GCM-SHA384
ECDHE-RSA-AES256-GCM-SHA384
ECDHE-RSA-AES256-SHA384
ECDHE-ECDSA-AES256-SHA384
ECDHE-RSA-AES128-GCM-SHA256
ECDHE-RSA-AES256-SHA
ECDHE-ECDSA-AES256-SHA
ECDHE-ECDSA-AES128-GCM-SHA256
ECDHE-RSA-AES128-SHA256
ECDHE-ECDSA-AES128-SHA256
ECDHE-RSA-AES128-SHA
ECDHE-ECDSA-AES128-SHA