Supported accounts are Microsoft, Exchange, Gmail and Outlook.com.
If you have more than one account set to sync contacts under Device Settings > Contacts (for iOS 10) or Settings > Accounts & Passwords (for iOS 11), then you will need to select iCloud as the Default Account in order to get the best experience with Outlook contact export. We do not officially support non-iCloud accounts (like Gmail) if they are set to Default Account.
