Using Outlook for iOS in business environments for email and scheduling
What I have is Apple Mail on my phone linked to Outlook/Hotmail so I can see my Outlook emails on my phone. Microsoft did a change that took effect on Sept 30 that basically broke that link - for authentication purposes they say. You may have an email from them in July and again about 3 weeks ago warning of this and offering fix suggestions. My Apple Mail fix was to delete and then re-install Outlook on the Apple Mail App. It worked - with my Archived emails on Apple Mail lost. The re-install seemed to do away with the IMAP on the “Incoming Mail Server” as part of the re-install. I don’t know about anything other than Apple Mail issues.