Magento 2.3: Account Email Confirmation is not sending

We are using Magento cloud environment for our project. There, we want to send a confirmation email when the customer get registered on our website.

So, I have done: Store -> Configuration -> Customers -> Customer Configuration -> Requires Email Confirmation -> Yes

Though, I have set the option to Yes, am not receiving any email when I register.

I have installed the Mageplaza SMTP extension and getting the test email without any issues.

So, I’m not sure, what could be the issue since its a default Magento config.

Any help will be appreciated!