Microsoft has fixed multi-factor authentication (MFA) for Office 365 on iPhones!
Law offices that were early adopters of Office 365 did not have a reliable way to enable multi-factor authentication for iPhones. Subsequently, these customers were given very long ‘app passwords’ to be used as a ‘backup password’ and maintained by the Office 365 administrator. This strategy has inherent security concerns.
Microsoft resolved the issue for deploying Multi-Factor Authentication on iPhones (and Outlook 2013 and later)! Now, after enabling ‘modern authentication’ in the admin console on older accounts, users simply need to remove and re-add their Office 365 email accounts. The process will employ multi-factor authentication and the old App Password can be deleted. This strategy significantly enhances security and is recommended.