The following behavior will be seen in published applications on Server 2016:
1. Publish an application such as Outlook to a Server VDA running Server 2016
2. Launch the published application with a user that has *never* launched a desktop session on that VDA. The significance of this will become apparent later in this article.
3. Click on any URL link within the application. If you are using Wordpad for your test you will get the following error “Wordpad was unable to open the URL. Check the URL and try again…”

4. If you are using Outlook or most other applications you will be prompted with the following:

This is by design. Citrix Metaframe Server FTA refers to a filter program for Host to Client Redirection – a feature that redirects URL launch requests from a VDA down to the default browser on the client. Users that want to take advantage of this feature should select Citrix Metaframe Server FTA, select the “Always use this app” checkbox if appropriate and click “OK”.
Note: Your Citrix Administrator will still need to enable the Citrix policy “Host to Client Redirection” for your account for this feature to be enabled.
5. What is not by design is that subsequent clicks on URLs within the published application, even in the same session, will continue to prompt with:

6. No matter how many times the user clicks the box for “Always use this app” the prompt will continue to display whenever a http or https link is invoked.
Related: