Intune Mobile Outlook Asking password again and again

Check if you've got a GPS based named location policy scoped to Exchange Online. That's expected behaviour, not a bug. Entra checks location through Authenticator about once an hour, and if Authenticator isn't installed or the user denied the location prompt, the claim never lands and Outlook just keeps asking. Teams works because it's not in scope of that policy.

Two other things that look the same: Android without proper Play Services fails Authenticator's integrity check, and GPS location doesn't work with passwordless at all.

Confirm it fast. Open a failed Outlook Mobile sign in, Conditional Access tab, GPS policy failing while compliance shows satisfied.

Fix wise, excluding a trusted device group works, but I'd use a device filter on an attribute rather than a static group since those go stale. Cleaner option is pulling Exchange Online out of the policy scope entirely. Microsoft's own guidance is to reserve GPS blocking for genuinely sensitive apps, and email rarely qualifies.