Craft Commerce not sending E-Mails immediately I have an e-mail problem at Craft Commerce. 
Emails are not sent at the time of purchase. 
The e-mail is only sent when you log in to the backend. 

I first thought it was a server queue problem. But the support of our Nginx server could not find any error. I have also already tried out various e-mail sending options.
Strangely enough, contact form e-mails are sent immediately and without delay. 

The problem occurred first when updating Craft Commerce.
Thanks to @PhilipBoomy for his answer.  The problem were missing cron jobs.

Additionally I want to add one more solution from the craft support team:

If you don't have the queue set up to run automatically with a cron job or worker, you can also try adding this to your order confirmation template:

{# run queue #}
{% do craft.app.queue.handleResponse %}
{{ craft.app.response.content|raw }}


Which will run the queue over Ajax on that page.