Currently, the Proton Mail iOS app does not let users add events from .ics calendar invitations to their Proton Calendar. On the web and Mac/desktop clients, opening an email with an .ics invite (including "METHOD:PUBLISH" invites that don't require a response) displays an "Add to Proton Calendar" button and allows the event to be imported directly. In the iOS Mail app, the .ics attachment is shown only as a file and there is no way to open it or import it into Proton Calendar.

Please add support in the Proton Mail iOS app to recognize .ics invitations (both meeting requests and PUBLISH reminders) and provide an "Add to Proton Calendar" button. This feature is essential for users who rely on Proton Calendar on iPhone/iPad and aligns iOS functionality with the existing functionality in web and desktop apps.