Error when update Cognito pool for a CustomEmailSender

Hi, I am trying to update an existing Cognito User Pool to make it send Emails using a third-party provider, I am following every detail mentioned in https://docs.aws.amazon.com/cognito/latest/developerguide/user-pool-lambda-custom-email-sender.html However when it comes to updating the pool using a CLI command "aws cognito-idp update-user-pool --lambda-config " I receive the following error:

Parameter validation failed: Unknown parameter in LambdaConfig: "CustomEmailSender", must be one of: PreSignUp, CustomMessage, PostConfirmation, PreAuthentication, PostAuthentication, DefineAuthChallenge, CreateAuthChallenge, VerifyAuthChallengeResponse, PreTokenGeneration, UserMigration Unknown parameter in LambdaConfig: "KMSKeyID", must be one of: PreSignUp, CustomMessage, PostConfirmation, PreAuthentication, PostAuthentication, DefineAuthChallenge, CreateAuthChallenge, VerifyAuthChallengeResponse, PreTokenGeneration, UserMigration

so what I understand is the CustomEmailSender is for some reason had been rejected as aparameter! and at same time this is not available in the console either.

I can set a CustomEmailSender only when i create a user pool using CloudFormation YAML script, but I am unable to update exisiting one

Help in this is highly appreciated.