Problems with some settings in Em Client for Android

First, I have a problem with a pop3 setup. I want to leave my mails on the server even if I delete them from inbox, but everytime a choose “Never”, after closing parameters and reopening choice is on “week”. It’s impossible to choose “never”.
I have no problem with Em client for windows.
Second problem: I cannot select all mails from inbox to change from unread to read,
Thanks for your help.

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