How can I mark all mails as read in a subbox?

Question

In order to view the questions in a timely fashion, I subscribe to some tags on SE, and created a label (subbox) in my Gmail named stackoverflow. I receive lots of unread mails day after day and now I want to mark all mails under this label as read in a quick way, but I didn't see any options in the menu to do this.

The maximum items in a page is 100, if I do this page by page, I need to go through 50 pages to mark all the mails. It would be time-consuming.

Any ideas?

Answer 1

You can click on the 'Subbox' and then use this:

That will match everything as read.

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To select every single email there, click on the checkbox on the top left then click the little 'popup':

Then mark everything as read.