Update custom-email.md

Adding the localize your email section

Author: yoelhor

articles/active-directory-b2c/custom-email.md

@@ -9,7 +9,7 @@ manager: celestedg
 ms.service: active-directory
 ms.workload: identity
 ms.topic: reference
-ms.date: 12/18/2019
+ms.date: 02/05/2020
 ms.author: marsma
 ms.subservice: B2C
 ---
@@ -387,6 +387,38 @@ For more information, see [Self-asserted technical profile](restful-technical-pr
 </ClaimsProvider>
 ```
 
+## [Optional] Localize your email
+
+The `GenerateSendGridRequestBody` claims transformation which generates the JSON payload, uses input claims that contain dynamic values (such as the email address and the OTP code), and static values (such as the template name, and email subject).
+
+To localize the email, you must send localized strings to SendGrid, or your email provider. For example to localize the email subject, body, your code message, and signature of the email. To do so, you can use the [GetLocalizedStringsTransformation](string-transformations.md) claims transformation to copy localized strings into claim types.
+
+1. In your policy define the following string claims: subject, message, codeIntro and signature.
+1. Define a [GetLocalizedStringsTransformation](string-transformations.md) claims transformation to substitute localized string values into the claims from step 1.
+1. Change the `GenerateSendGridRequestBody` technical profile to use input claims with the following XML snippet.
+1. Update your SendGrind template to use dynamic parameters in place of all the strings which will be localized by Azure AD B2C.
+
+```XML
+<ClaimsTransformation Id="GenerateSendGridRequestBody" TransformationMethod="GenerateJson">
+  <InputClaims>
+    <InputClaim ClaimTypeReferenceId="email" TransformationClaimType="personalizations.0.to.0.email" />
+    <InputClaim ClaimTypeReferenceId="subject" TransformationClaimType="personalizations.0.dynamic_template_data.subject" />
+    <InputClaim ClaimTypeReferenceId="otp" TransformationClaimType="personalizations.0.dynamic_template_data.otp" />
+    <InputClaim ClaimTypeReferenceId="email" TransformationClaimType="personalizations.0.dynamic_template_data.email" />
+    <InputClaim ClaimTypeReferenceId="message" TransformationClaimType="personalizations.0.dynamic_template_data.message" />
+    <InputClaim ClaimTypeReferenceId="codeIntro" TransformationClaimType="personalizations.0.dynamic_template_data.codeIntro" />
+    <InputClaim ClaimTypeReferenceId="signature" TransformationClaimType="personalizations.0.dynamic_template_data.signature" />
+  </InputClaims>
+  <InputParameters>
+    <InputParameter Id="template_id" DataType="string" Value="d-1234567890" />
+    <InputParameter Id="from.email" DataType="string" Value="[email protected]" />
+  </InputParameters>
+  <OutputClaims>
+    <OutputClaim ClaimTypeReferenceId="sendGridReqBody" TransformationClaimType="outputClaim" />
+  </OutputClaims>
+</ClaimsTransformation>
+```
+
 ## Next steps
 
 You can find an example of a custom email verification policy on GitHub: