External user with personal email domain cannot sign in to Azure DevOps

Question

We are facing an issue with external user trying to sign in to Azure DevOps.

Uses who sign in with public email providers such as gmail.com or outlook.com can access Azure DevOps without any problems. However, users who use a personal or custom email domain fail during the sign-in process.

The error shown at login is: "We couldn’t find an account with that username”

Current setup:

• Guest access is enabled in Azure DevOps
• The user is added to the Azure DevOps organization
• The correct Azure DevOps organization URL is used
• No Conditional Access policies are blocking guest users

What we see:

• Public domains (gmail.com, outlook.com) work as expected
• Personal or custom domains always fail with the “account not found” error

We would appreciate your assistance in investigating this issue and advising on the correct configuration to resolve it.We are facing an issue with external user trying to sign in to Azure DevOps.

Uses who sign in with public email providers such as gmail.com or outlook.com can access Azure DevOps without any problems. However, users who use a personal or custom email domain fail during the sign-in process.

The error shown at login is: "We couldn’t find an account with that username”

Current setup:

• Guest access is enabled in Azure DevOps
• The user is added to the Azure DevOps organization
• The correct Azure DevOps organization URL is used
• No Conditional Access policies are blocking guest users

What we see:

• Public domains (gmail.com, outlook.com) work as expected
• Personal or custom domains always fail with the “account not found” error

We would appreciate your assistance in investigating this issue and advising on the correct configuration to resolve it.

Answer 1

Hi @Dmitrijs Balickis

Thank you for reaching out to Microsoft Q&A.

The issue occurs due to the way Azure DevOps handles authentication for external users based on their email domain and identity type. Azure DevOps supports sign-in using either Microsoft personal accounts (such as gmail.com or outlook.com) or Microsoft Entra ID (Azure AD) accounts. Public email domains like Gmail and Outlook are treated as Microsoft personal accounts and can authenticate directly without additional configuration. However, users with personal or custom email domains (for example, ******@customdomain.com) are assumed to belong to a Microsoft Entra tenant. In such cases, Azure DevOps expects these users to exist as Microsoft Entra B2B guest users in the organization’s tenant. If the guest identity is not created correctly, the invitation is not accepted, or there is a mismatch between the user’s Entra ID identity and what is added in Azure DevOps, the sign-in fails with the error “We couldn’t find an account with that username.” This is expected behavior when the Azure DevOps organization is backed by Microsoft Entra ID and the external user has not been properly onboarded as a B2B guest.

Refer below points to resolve this issue or this is the workaround:

1. Invite the external user as a Guest in Microsoft Entra ID Ensure the external user with a personal or custom email domain is first invited to your Microsoft Entra ID tenant as a B2B guest user from the Azure portal (Microsoft Entra ID → Users → New guest user). The user must accept the invitation before they can access Azure DevOps. Without an accepted guest identity, Azure DevOps cannot resolve the account during sign-in.

2. Verify the guest user identity in Entra ID After the invitation is accepted, confirm that the guest user exists in Microsoft Entra ID and has a valid guest UPN (typically in the format username_domain.com#EXT#@yourtenant.onmicrosoft.com). Azure DevOps relies on this guest object for authentication, and any mismatch can result in an “account not found” error.

3. Add the guest user to the Azure DevOps organization Once the guest user is present in Entra ID, add the same email address to the Azure DevOps organization (Organization Settings → Users) and assign the appropriate access level (Stakeholder or Basic). This step should be done after the guest user has been successfully created in Entra ID.

4. Ensure the user signs in with the correct account type Ask the external user to sign in using the “Work or school account” option and access the correct Azure DevOps organization URL (https://dev.azure.com/{organization}). Using an incorrect sign-in option or cached credentials can also trigger the error.

5. Clear cached credentials if needed If the issue persists, have the user sign out completely using https://aka.ms/vssignout and then retry the sign-in in a new InPrivate or Incognito browser session to avoid cached identity conflicts.