Hi @Huw Werrett ,
MS365 Outlook Contacts and Calendar won't synch with IPhone Contacts and Calendar.
To verify, are you having trouble syncing contact and calendar with Outlook for iOS?or with your iPhone?
If it is a synchronization problem between the iPhone's contacts and calendar, please refer to this article: Synchronize Outlook and Apple iPhone or iPod touch calendars
During this process, if you encounter synchronization problems, please contact apple support.
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