Several rules in my GMail account apply various labels to mails and mostly archive them right away. This is handy for newsletters, mailing lists and the like. However over time - if you do not read them all - there are unread mails, scattered around several labels which are too old to show on the first 50 items.
Up to now I sometimes went through the following pages, using the "Select unread" and "Mark as read" functions. Today I stumbled across a page that mentions a search term to show only unread mails. I had suspected something like this must exist, but there is no GUI feature I know of to use it.
So in addition to any other search criteria you might have (e. g. "label:newsletter") you can just add "is:unread" and only get those mails that you haven't looked at before. Other things I just tried out and found to work:
- is:starred - applies to messages with stars.
- is:unread - applies to unread messages
- is:read - applies to read messages