It is possible to distribute your Enterprise app using third-party MDM products such as MobileIron, to name one example.
If you choose to host the files for distribution yourself however, there are a few requirements that you need to consider. The three key requirements for hosting Enterprise IPA installation files are:
- IPA files need to be hosted behind HTTPS otherwise the IPA file will fail to install.
- The installations files and directory folder where they are located need to have appropriate file permissions, e.g. at least 0555.
- If using a .php file for the installation, the web servers need .php support. If the server does not support .php, an alternative set-up is possible, but that requires separate installation links for each of the app file types (if you are also hosting apps for desktop, Android, etc.), rather than a single installation link for all versions of the app.
- According to Apple’s terms and conditions, the web server should be a secure server that only authenticated users can access, i.e. it should be password protected. From Apple’s Enterprise Guidelines, “You may permit Your Permitted Entity to deploy Your Internal Use Applications to Permitted Users on Your behalf, provided that such deployment is at least as restrictive and protective of Apple as the terms of this Agreement (e.g., posting the App on a public website or non-authenticated server would be prohibited).”
If you are running iOS 9 or higher on your iOS device, after installation of the app, you will need to go to Settings > General > Profiles and trust the associated developer/company. You will then be able to launch the app.