The popup window notify for new mails but it will not close automatically after open and read the new mails.

Would it be possible to add an option to automatically close the popup after open the inbox?

I assume you are talking about the Telltale popup. Mine closes automatically but not until a message is opened and then closed. I keep my New Mail folder open so my preference would be that the Telltale popup close as soon as an unread message from the New Mail folder is opened.

I work in List mode. In Preview mode it should close when an unread message in the NMF is selected.

I work in list mode, too. Further my Pmail is opened the whole day but minimized to system tray bar. Once a new mail arrives, the telltale popup appears and the Pmail horse in the sys tray is flapping its wings. But as soon as this new mail has been opened and read followed by minimizing Pmail again, the telltale popup disappears again and automatically. No problem with it.

Ah ok, I normally not minimize Pmail, it is running most time on desktop background.
But you are right when minimizing it then the popup will disapear.

Never the less, would be nice if it will close directly when I read the new mail.