serverless.yml

custom:   
   appSync:
      mappingTemplates:
         - type: Mutation
           dataSource: AWSSES
           field: sendNotification
           request: Mutation-sendNotification-request.vtl
           response: Mutation-sendNotification-response.vtl
      dataSources:
         - type: HTTP
           name: AWSSES
           description: "send email notification"
           config:
             endpoint: "https://email.us-east-1.amazonaws.com/"
             authorizationConfig:
               authorizationType: "AWS_IAM"
               awsIamConfig:
                 signingRegion: "us-east-1"
                 signingServiceName: "ses"
             serviceRoleArn: { Fn::GetAtt: [AppSyncSESserviceRole, Arn] }