Mail app stopped functioning after iOS update

My company has about 1,000 iOS supervised devices, all of which are supervised and ran through the HTTP proxy server (content filtering). Before the recent update, everything was working out smoothly – Mail app works exactly as it should, emails are sent and received, and reports are gathered in real-time. With the newest update, we get status bar icon, saying “Connecting” endlessly if we try to fetch new messages. All other mail accounts work (Gmail, Outlook) but the iOS Mail app does not. What is going on and how should we approach this problem?

hey there!
In this link you can find information about it and how to fix it