Azure AD B2C - "emails" claim in custom policy - azure-ad-b2c

Question

I'm looking for a way to add an emails claim (collection of emails) to a custom policy for Azure AD B2C. This application claim is available from the Azure Portal directly but I cannot find a way to implement this in a custom policy which I need to create.
What I want to achieve is to have Azure AD B2C authentication for my WebApp users and Azure AD authentication as custom Authentication Provider for employees so It means I will need to add emails claim twice - for Local accounts and for Azure AD.
I followed this guide to make custom policy so I've added a new ClaimsProvider to TrustFrameworkExtensions.xml file.
When I download Sign Up & Sign In policy created in Azure Portal then I can see the following Output Claim:
<OutputClaim ClaimTypeReferenceId="emails" />
I tried to put that line to my custom policy but it does not return emails claim.
Any ideas?

Answer 1

I couldn't find an answer this either - it looks like the "emails" claim is being returned by a custom OutputClaimsTransformation, the configuration of which isn't available in the samples.
I did find the this answer on SO which helped, but it covers updated the "otherMails" claim for NEW users and I had existing users on the basic policies who I couldn't update in that way.
It seems that emails is being populated by concatenating "otherMails" (in the case of social signups) with the first entry in the "signInNames" array.
I ended up doing the following to get the "emails" claim dynamically created.
Create two new ClaimTypes in TrustFrameworkExtensions.xml
<ClaimType Id="emails">
<DisplayName>Emails</DisplayName>
<DataType>stringCollection</DataType>
<UserHelpText>User's email addresses</UserHelpText>
</ClaimType>
<ClaimType Id="firstOtherMail">
<DisplayName>First Other mail</DisplayName>
<DataType>string</DataType>
<UserHelpText>Other Mail</UserHelpText>
</ClaimType>
Create 3 new ClaimsTransformations in TrustFrameworkExtensions.xml
<ClaimsTransformation Id="GetFirstOtherMail" TransformationMethod="GetSingleItemFromStringCollection">
<InputClaims>
<InputClaim ClaimTypeReferenceId="otherMails" TransformationClaimType="collection" />
</InputClaims>
<OutputClaims>
<OutputClaim ClaimTypeReferenceId="firstOtherMail" TransformationClaimType="extractedItem" />
</OutputClaims>
</ClaimsTransformation>
<ClaimsTransformation Id="CopyFirstOtherMailToEmail" TransformationMethod="AddItemToStringCollection">
<InputClaims>
<InputClaim ClaimTypeReferenceId="firstOtherMail" TransformationClaimType="item" />
<InputClaim ClaimTypeReferenceId="emails" TransformationClaimType="collection" />
</InputClaims>
<OutputClaims>
<OutputClaim ClaimTypeReferenceId="emails" TransformationClaimType="collection" />
</OutputClaims>
</ClaimsTransformation>
<ClaimsTransformation Id="CopySignInNamesEmailToEmails" TransformationMethod="AddItemToStringCollection">
<InputClaims>
<InputClaim ClaimTypeReferenceId="signInNames.emailAddress" TransformationClaimType="item" />
<InputClaim ClaimTypeReferenceId="emails" TransformationClaimType="collection" />
</InputClaims>
<OutputClaims>
<OutputClaim ClaimTypeReferenceId="emails" TransformationClaimType="collection" />
</OutputClaims>
</ClaimsTransformation>
Create a new TechnicalProfile in TrustFrameworkExtensions.xml:
<!-- The following technical profile is used to create the emails collection after user authenticates. -->
<TechnicalProfile Id="AAD-UserCreateEmailsClaim">
<Metadata>
<Item Key="Operation">Read</Item>
<Item Key="RaiseErrorIfClaimsPrincipalDoesNotExist">true</Item>
</Metadata>
<IncludeInSso>false</IncludeInSso>
<InputClaims>
<InputClaim ClaimTypeReferenceId="objectId" Required="true" />
</InputClaims>
<OutputClaims>
<OutputClaim ClaimTypeReferenceId="emails" />
</OutputClaims>
<OutputClaimsTransformations>
<OutputClaimsTransformation ReferenceId="GetFirstOtherMail"/>
<OutputClaimsTransformation ReferenceId="CopySignInNamesEmailToEmails"/>
<OutputClaimsTransformation ReferenceId="CopyFirstOtherMailToEmail"/>
</OutputClaimsTransformations>
<IncludeTechnicalProfile ReferenceId="AAD-Common" />
</TechnicalProfile>
Add a new OrchestrationStep to the SignUpOrSignIn UserJourney just before the last step (SendClaims) in SignUpOrSignIn
<OrchestrationStep Order="8" Type="ClaimsExchange">
<ClaimsExchanges>
<!-- create the emails claim combining signInNames and otherMails -->
<ClaimsExchange Id="AADUserCreateEmailsClaim" TechnicalProfileReferenceId="AAD-UserCreateEmailsClaim" />
</ClaimsExchanges>
</OrchestrationStep>
<OrchestrationStep Order="9" Type="SendClaims" CpimIssuerTechnicalProfileReferenceId="JwtIssuer" />
Edit the PolicyProfile TechnicalProfile and add the OutputClaim:
<OutputClaim ClaimTypeReferenceId="emails" />

Answer 2

I took a much simpler route, and just added the following output claim in the SignInSignUp.xml (I left the existing email output claim in, that anyway gets populated only for social sign-ins)
<OutputClaim ClaimTypeReferenceId="signInNames.emailAddress" PartnerClaimType="email" />