How to share calendar from Shared mailbox to mobile app

The behavior fits Outlook mobile’s sharing model: adding a shared mailbox exposes its main calendar, while additional calendar folders need to be shared and accepted separately. Mailbox membership may not add secondary calendars to mobile.

In Outlook on the web, open the shared mailbox, go to Calendar, select each additional calendar, then open Sharing and permissions. Add each member with Can edit or the minimum required view permission. Each person should accept the invitations in Outlook on the web or Outlook mobile. In mobile, open Calendar, tap the plus button, choose Add a shared calendar, and search for the mailbox or calendar. Restart Outlook if an accepted calendar remains missing.

For visual separation, each member can choose a different display color from the calendar gear menu. Microsoft does not document a tenant-wide setting that forces identical calendar colors on mobile clients, so categories will not provide centrally consistent colors.