UserPrincipalName policies that apply to all user accounts
Every user account that needs to sign in to the Azure AD authentication system must have a unique user principal name (UPN) attribute value associated with that account. The following table outlines the polices that apply to both on-premises Active Directory-sourced user accounts (synced to the cloud) and to cloud-only user accounts.
A – Z
0 – 9
. - _ ! # ^ \~
Characters not allowed
Any '@' character that is not separating the user name from the domain.
Cannot contain a period character '.' immediately preceding the '@' symbol
Total length must not exceed 113 characters
64 characters before the ‘@’ symbol
48 characters after the ‘@’ symbol
Password policies that apply only to cloud user accounts
The following table describes the available password policy settings that can be applied to user accounts that are created and managed in Azure AD.