To set up the New Mail module, use the instructions: https://solomono.net/en/modul-novaja-pochta-api-a-528.html
Go to the section "Modules" -> "Delivery" -> "Delivery modules" -> "New mail" and click on the "edit" icon:
after in the modal window, click all the "Update ..." buttons:
The field with "API Key" must be filled in:
Important! The key that you received during registration has an expiration date, it is indicated in your IR account. The key needs to be updated if the term expires. To do this, follow the same steps as when generating a new key, all steps are written in the instructions: https://solomono.net/en/modul-novaja-pochta-api-a-528.html