Can anyone tell me why the built-in e-mail app doesnt work descent?

when ive read email, close the app and start it back up most of the time emails allready been read are again unread. messages removed are back in the list unread. and clicking on the notification and read all the mails and shut down the email app doesnt record the read emails. when you open the email client again everything is back to unread.

This thing is annoying me big time..... Spam i removed is back in the mail several times before its really deleted. its highly anoying!