iPhone Unable to Add 365 Account After Password Change – Hybrid Exchange

Hi all,

We have an Exchange Hybrid setup. All mailboxes are hosted in Exchange Online, and our on-prem Exchange server is only used for SMTP relay (e.g., for MFPs). One of our users is currently unable to add their account to their iPhone. It was working fine until a few days ago.

The issue started right after the user changed their password. Since then, the Outlook app or Office apps on the iPhone doesn't accept the user's credentials. However, everything works perfectly fine on their PC and even on another test iPhone using the same credentials. It validate the credentials but then throws a generic error after entering credentials.

What we’ve tried so far:

Resetting the user’s MFA settings
Resetting the password again
Excluding the user from MFA temporarily
Factory resetting the iPhone

Despite all that, the issue persists. Since the account works on a different iPhone, and even a full reset didn’t resolve it on the affected device, I’m at a bit of a loss.

Has anyone encountered this or have any ideas? Any suggestions would be much appreciated.

Thanks in advance!