Currently, Portal does not support Microsoft Modern Authentication when configuring email settings within Portal. Portal only supports basic/legacy authentication. This presents multiple problems because Microsoft is deprecating legacy authentication in April of 2026.
Without Modern Authentication support, it will be impossible for organizations to configure Portal Email Settings which also means it will be impossible for organizations to implement MFA for their built-in Portal accounts (because even configuring MFA requires the Portal emailer to be configured).
So at minimum, once legacy authentication is deprecated (for those who use Microsoft email), Portal's emailer will be broken. And even worse, MFA will not be able to be configured because it requires the Portal Emailer to be configured first (although maybe Portal doesn't care if the emailer actually works for MFA to function, I'm not sure).
Not being able to configure MFA goes directly against Esri's hardening guide for ArcGIS Enterprise. So ideally, we'd like Esri to support Microsoft Modern Authentication so we can implement the security best practices that Esri recommends. Note that changing email providers or using non-built-in accounts might not be an acceptable solution for everyone.
