diff --git a/src/OpenIddict.Core/OpenIddictManager.cs b/src/OpenIddict.Core/OpenIddictManager.cs
index d7a60e31..e090d7a2 100644
--- a/src/OpenIddict.Core/OpenIddictManager.cs
+++ b/src/OpenIddict.Core/OpenIddictManager.cs
@@ -68,15 +68,17 @@ namespace OpenIddict {
             // access tokens, even if an explicit destination is not specified.
             identity.AddClaim(ClaimTypes.NameIdentifier, await Services.Users.GetUserIdAsync(user));
 
-            // Resolve the username and the email address associated with the user.
-            var username = await Services.Users.GetUserNameAsync(user);
-            var email = await Services.Users.GetEmailAsync(user);
+            // Resolve the email address associated with the user if the underlying store supports it.
+            var email = Services.Users.SupportsUserEmail ? await Services.Users.GetEmailAsync(user) : null;
 
             // Only add the name claim if the "profile" scope was granted.
             if (scopes.Contains(OpenIdConnectConstants.Scopes.Profile)) {
+                var username = await Services.Users.GetUserNameAsync(user);
+
                 // Throw an exception if the username corresponds to the registered
                 // email address and if the "email" scope has not been requested.
                 if (!scopes.Contains(OpenIdConnectConstants.Scopes.Email) &&
+                    !string.IsNullOrEmpty(email) &&
                      string.Equals(username, email, StringComparison.OrdinalIgnoreCase)) {
                     throw new InvalidOperationException("The 'email' scope is required.");
                 }
@@ -87,7 +89,7 @@ namespace OpenIddict {
             }
 
             // Only add the email address if the "email" scope was granted.
-            if (scopes.Contains(OpenIdConnectConstants.Scopes.Email)) {
+            if (!string.IsNullOrEmpty(email) && scopes.Contains(OpenIdConnectConstants.Scopes.Email)) {
                 identity.AddClaim(ClaimTypes.Email, email,
                     OpenIdConnectConstants.Destinations.AccessToken,
                     OpenIdConnectConstants.Destinations.IdentityToken);
@@ -96,8 +98,8 @@ namespace OpenIddict {
             if (Services.Users.SupportsUserRole && scopes.Contains(OpenIddictConstants.Scopes.Roles)) {
                 foreach (var role in await Services.Users.GetRolesAsync(user)) {
                     identity.AddClaim(identity.RoleClaimType, role,
-                    OpenIdConnectConstants.Destinations.AccessToken,
-                    OpenIdConnectConstants.Destinations.IdentityToken);
+                        OpenIdConnectConstants.Destinations.AccessToken,
+                        OpenIdConnectConstants.Destinations.IdentityToken);
                 }
             }
 
diff --git a/src/OpenIddict.Core/OpenIddictProvider.Authentication.cs b/src/OpenIddict.Core/OpenIddictProvider.Authentication.cs
index acee2c1d..d188b1ad 100644
--- a/src/OpenIddict.Core/OpenIddictProvider.Authentication.cs
+++ b/src/OpenIddict.Core/OpenIddictProvider.Authentication.cs
@@ -79,16 +79,19 @@ namespace OpenIddict {
 
                 // Return an error if the username corresponds to the registered
                 // email address and if the "email" scope has not been requested.
-                if (context.Request.HasScope(OpenIdConnectConstants.Scopes.Profile) &&
-                   !context.Request.HasScope(OpenIdConnectConstants.Scopes.Email) &&
-                    string.Equals(await services.Users.GetUserNameAsync(user),
-                                  await services.Users.GetEmailAsync(user),
-                                  StringComparison.OrdinalIgnoreCase)) {
-                    context.Reject(
-                        error: OpenIdConnectConstants.Errors.InvalidRequest,
-                        description: "The 'email' scope is required.");
-
-                    return;
+                if (services.Users.SupportsUserEmail && context.Request.HasScope(OpenIdConnectConstants.Scopes.Profile) &&
+                                                       !context.Request.HasScope(OpenIdConnectConstants.Scopes.Email)) {
+                    // Retrieve the username and the email address associated with the user.
+                    var username = await services.Users.GetUserNameAsync(user);
+                    var email = await services.Users.GetEmailAsync(user);
+
+                    if (!string.IsNullOrEmpty(email) && string.Equals(username, email, StringComparison.OrdinalIgnoreCase)) {
+                        context.Reject(
+                            error: OpenIdConnectConstants.Errors.InvalidRequest,
+                            description: "The 'email' scope is required.");
+
+                        return;
+                    }
                 }
             }
 
diff --git a/src/OpenIddict.Core/OpenIddictProvider.Exchange.cs b/src/OpenIddict.Core/OpenIddictProvider.Exchange.cs
index 236830ce..8db5512e 100644
--- a/src/OpenIddict.Core/OpenIddictProvider.Exchange.cs
+++ b/src/OpenIddict.Core/OpenIddictProvider.Exchange.cs
@@ -234,16 +234,19 @@ namespace OpenIddict {
 
             // Return an error if the username corresponds to the registered
             // email address and if the "email" scope has not been requested.
-            if (context.Request.HasScope(OpenIdConnectConstants.Scopes.Profile) &&
-               !context.Request.HasScope(OpenIdConnectConstants.Scopes.Email) &&
-                string.Equals(await services.Users.GetUserNameAsync(user),
-                              await services.Users.GetEmailAsync(user),
-                              StringComparison.OrdinalIgnoreCase)) {
-                context.Reject(
-                    error: OpenIdConnectConstants.Errors.InvalidRequest,
-                    description: "The 'email' scope is required.");
+            if (services.Users.SupportsUserEmail && context.Request.HasScope(OpenIdConnectConstants.Scopes.Profile) &&
+                                                   !context.Request.HasScope(OpenIdConnectConstants.Scopes.Email)) {
+                // Retrieve the username and the email address associated with the user.
+                var username = await services.Users.GetUserNameAsync(user);
+                var email = await services.Users.GetEmailAsync(user);
 
-                return;
+                if (!string.IsNullOrEmpty(email) && string.Equals(username, email, StringComparison.OrdinalIgnoreCase)) {
+                    context.Reject(
+                        error: OpenIdConnectConstants.Errors.InvalidRequest,
+                        description: "The 'email' scope is required.");
+
+                    return;
+                }
             }
 
             var identity = await services.Applications.CreateIdentityAsync(user, context.Request.GetScopes());
diff --git a/src/OpenIddict.Core/OpenIddictProvider.Userinfo.cs b/src/OpenIddict.Core/OpenIddictProvider.Userinfo.cs
index cc1ae11f..3862727e 100644
--- a/src/OpenIddict.Core/OpenIddictProvider.Userinfo.cs
+++ b/src/OpenIddict.Core/OpenIddictProvider.Userinfo.cs
@@ -50,7 +50,7 @@ namespace OpenIddict {
             }
 
             // Only add the email address details if the "email" scope was present in the access token.
-            if (context.Ticket.HasScope(OpenIdConnectConstants.Scopes.Email)) {
+            if (services.Users.SupportsUserEmail && context.Ticket.HasScope(OpenIdConnectConstants.Scopes.Email)) {
                 context.Email = await services.Users.GetEmailAsync(user);
 
                 // Only add the "email_verified" claim
@@ -61,7 +61,8 @@ namespace OpenIddict {
             };
 
             // Only add the phone number details if the "phone" scope was present in the access token.
-            if (context.Ticket.HasScope(OpenIdConnectConstants.Scopes.Phone)) {
+            if (services.Users.SupportsUserPhoneNumber &&
+                context.Ticket.HasScope(OpenIdConnectConstants.Scopes.Phone)) {
                 context.PhoneNumber = await services.Users.GetPhoneNumberAsync(user);
 
                 // Only add the "phone_number_verified"