I dont understand the cause of "Could not notify user by email" error when i create a user

General
1

I am getting a fault saying “Unable to register user due to error: Could not notify user by email” this is my code(written in kotlin).

override fun createUserAccount(@NonNull username: String,@NonNull password: String,
                               @NonNull email: String,@NonNull userEvents: UserEventListener.UserSignUpEventListener) {

    val backendlessUser: BackendlessUser = BackendlessUser()
    backendlessUser.email = email
    backendlessUser.password = password
    backendlessUser.setProperty(Defaults.USERNAME_PARAM, username)

    Backendless.UserService.register(backendlessUser, object : AsyncCallback<BackendlessUser> {
        override fun handleResponse(response: BackendlessUser) {
            userEvents.onUserCreated(User.convertToLocal(backendlessUser))
        }

        override fun handleFault(fault: BackendlessFault) {
            userEvents.onError(fault)
        }
    })
}

override fun loginUser(@NonNull username: String,@NonNull password: String,
                       @NonNull userEvents: UserEventListener.UserSignInEventListener) {
    Backendless.UserService.login(username, password, object : AsyncCallback<BackendlessUser> {
        override fun handleResponse(response: BackendlessUser?) {
            userEvents.onUserLoggedin(User.convertToLocal(response))
        }

        override fun handleFault(fault: BackendlessFault) {
            userEvents.onError(fault)
        }
    })
}
companion object Converter {
    internal fun convertToLocal(remoteUser: BackendlessUser?): User {

        val user: User = User()
        user.objectId = remoteUser?.objectId
        user.created = remoteUser?.getProperty(Defaults.CREATED_PARAM) as Date
        user.updated = remoteUser.getProperty(Defaults.UPDATED_PARAM) as Date
        user.email = remoteUser.email
        user.name = remoteUser.getProperty(Defaults.USERNAME_PARAM) as String
        user.password = remoteUser.password
        user.avatartUrl = remoteUser.getProperty(Defaults.URL_PARAM) as String
        user.followers = remoteUser.getProperty(Defaults.FOLLOWERS_PARAM) as List<BackendlessUser>
        return user
    }

    internal fun convertToRemote(localUser: User?): BackendlessUser {

        val user: BackendlessUser = BackendlessUser()
        user.setProperty(Defaults.OBJECTID_PARAM, localUser?.objectId)
        user.setProperty(Defaults.CREATED_PARAM, localUser?.created)
        user.setProperty(Defaults.UPDATED_PARAM, localUser?.updated)
        user.email = localUser?.email
        user.setProperty(Defaults.USERNAME_PARAM, localUser?.name)
        user.password = localUser?.password
        user.setProperty(Defaults.URL_PARAM, localUser?.avatartUrl)
        user.setProperty(Defaults.FOLLOWERS_PARAM, localUser?.followers)
        return user
    }
}
2

There may be a couple of reasons:

    Do you have custom email settings in the backend configuration? Email confirmations are turned on (Users > Registration > Require Email Confirmation) and the email user registered with is not valid.
Regards, Mark