Gmail IMAP

One more problem solved. If you are in a situation where you check email in multiple devices, and it is not in sync. Having to do it twice or more, read all new messages and classified on your phone already, again on your laptop mail app, and the email on your web base gmail is still mark unread, try IMAP instead of POP. You only have to do it once...
Read more at Getting Gmail anywhere: IMAP versus POP