Beginning January 12, 2016, only the most current version of Internet Explorer available for a supported operating system will receive technical support and security updates.
You can find this “most current version … for a supported OS” here:
The most interesting section might be the “Desktop” and here you can see that only Vista is limited to a Version lower then IE11. But Vista it self is out of Support since April 11 2017: https://support.microsoft.com/de-de/help/22882/windows-vista-end-of-support and you can read there that using the IE 9 on Vista “setzen Sie den PC möglicherweise zusätzlichen Bedrohungen aus”.
The Server section show a mix of versions from IE 9-11. So, an administrator that sits on his desktop computer and logs on to an remote server might surf there with an old IE 9-10. But I think he will have to skill to realize that, if there are things not so nice, that he can use the IE on his Desktop to get better results.
I never used one of this and can't say anything about it. Is there a realistic number of users to take care of?