Low severityauthentication
Power BI Error:
AADSTS90101, Invalid Email Format During Sign-In
What does this error mean?
The username submitted to Azure AD / Entra ID isn't formatted as a valid email address (someone@example.com).
Common causes
- 1User typed an incomplete or malformed address (missing @, missing domain, trailing space, smart-quote characters)
- 2Application sends a SAM account name, employee ID, or display name to the /authorize endpoint instead of the UPN
- 3login_hint or username_hint parameter contains an unencoded or invalid value
- 4Custom sign-in form pre-fills the username field from a CRM/HR field that isn't a UPN
- 5Federated/B2B guest user signing in with their on-prem alias instead of their UPN/email
How to fix it
- 1Re-enter the full email/UPN in the format someone@example.com — check for typos, missing domain (@contoso.com), and stray spaces or pasted smart quotes
- 2If the value is being sent by an app (login_hint, username param), inspect the auth request and confirm a valid UPN is passed — not a SAM name, employee ID, or display name
- 3For guest/B2B users, sign in with the UPN from your home tenant (the address that received the invitation), not a local alias
- 4If using a custom sign-in page or embedded Power BI scenario, validate the username field client-side against an email regex before redirecting to login.microsoftonline.com
- 5If the error fires for a federated user, verify the UPN suffix is a verified domain in Entra ID (Microsoft Entra admin center → Custom domain names)