To improve security, we are going to be disabling the deprecated TLS 1.0 and 1.1 protocols. The effect for end users should be minimal as all current devices and operating systems support at least TLS 1.2.
After this change, Zimbra will support only TLS 1.2 and 1.3.
The globalsign.com compatibility table provides a clear and useful list of affected versions:
For anyone who is still using Windows 7 - which is no longer supported by Microsoft, it is possible to enable TLS1.2 using the KB 3140245 update (https://support.microsoft.com/help/3140245). Windows 8 and newer already support TLS 1.2.
Once we commence this work, all incoming email will be queued, access to the Zimbra servers will be restricted, and Zimbra customers will not be able to access their mailboxes.
The capabilities of the control panel to provision and manage services will also be restricted.