"Reading Emails" to my opinion this is functioning wrong:
After reading a mail, the mailbox closes completely closing the mailbox in the progress. This means you have to open the mailbox AGAIN to delete the read email or read the next email.
to make the mailbox function better, there should also be a delete button to remove the opened email and go back to the inbox.
The close button should only close the opened email and go back to the inbox.
An additional option could be a button called "Close&Exit" which would close the opened email and exit the mailbox without deleting the email.
Thanks for reading