The email section in Order type settings page is replaced by symfony mailer thus removing the "Email the customer a receipt when an order is placed" checkbox.
So if a user has checked this setting before and decided to use symfony mailer to manage all e-mails, there is no way to uncheck this setting unless removing the module. (Or manual config update and drush cim).
The problem with this scenario is there is always an e-mail sent by commerce itself when an order is placed.
We should have an option to manage this maybe in the UI or with a default behavior where if symfony mailer is installed this option should be unchecked or something.
Fixed
1.4
User interface