I have thousands of unread messages in gmail, and it is messing with my iPhone. How do I mark all messages as "read" as I would do in Outlook?

In Gmail, click on the gear symbol (top right) and choose mail settings.

Click on filters.

Create a new filter (you see this option at the bottom of the page).

In the "Has the words" box, type is:unread

Click Create filter with this search

Ignore the warning, click OK

Tick the following boxes:



And choose create filter.

That will mark all your messages as read!