How to reproduce
Select an email in the inbox.
Click on button "delete".
Actual results:
The email is directly and irreversibly deleted.
It is not possible to restore the email.
Expected results:
When clicking on the button "delete" the emails are moved to folder "trash".
From this folder it is possible to restore the emails.
When an email is already in the folder "trash", clicking on "delete" results in completely/irreversibly deleting the email.
Solution:
The problem can be tackled by changing the server settings.
But the default should be changed so that deleted emails always appear in the file "trash" as expected.
(cf. fault tolerance)