So im writing this discussion cuase i wanna know if there are any way, that we (The IT-Administration) of this company can admninistrate the signatures that our emplyess have on their outlook, both on their android/iphone and their computers?
You can use mail flow rules to handle that. This method is not perfect, but might be a bit better than letting each and every employee set up signatures on their own. Here's a video tutorial which shows the setup process. The mail flow rule creator has been redesigned recently, but you can get the general idea on how to get the task done.