Follow along with the video below to see how to install our site as a web app on your home screen.
Note: This feature currently requires accessing the site using the built-in Safari browser.
If you are still using CentOS 7.9, it's time to convert to Alma 8 with the free centos2alma tool by Plesk or Plesk Migrator. Please let us know your experiences or concerns in this thread: CentOS2Alma discussion
I dont know if you can disable the page, but you can disable webmail on a per domain basis. It can be found in the domain under mail > mail preferences.
Edit: Also, you can remove the DNS record for "webmail" in that domain. That will prevent anyone from seeing a horde login page. (apache redirects urls starting with webmail.* to the horde login)