Adding MFA protection to the Exchange ActiveSync IIS site causes authentication failures on mobile devices.
Symantec VIP IIS integration offers MFA support for many IIS applications, including Outlook Web Access, AD FS for IIS, etc. Due to limitations with Exchange ActiveSync, adding VIP MFA protection to ActiveSync isn't a supported option.
Optionally, the Outlook apps for iOS and Android are cloud-backed applications that integrate Modern Authentication access controls. VIP natively integrates with Microsoft AD FS and Microsoft Azure AD to allow for
strong authentication into Outlook and other Microsoft 365 applications.