A new release of SimpleCart is now available as pre-release.
SimpleCart 2.8 changes the way (re)sending email confirmations and processing the order works, so that it can be called from asynchronous payment confirmations. This has been a long-standing issue where webhooks would get called, but they only marked orders as paid and would not actually process any of the hooks or send email notifications.
With this update, plus an update to the Mollie gateway, that should now work much better out of the box. If you’ve previously worked around this issue, for example with a cron job or custom gateways, please test this release and make sure it works as expected.