Using search options in email instead of folders is the biggest advantage of the Gmail wonder, but I first got used to this in GroupWise where I stopped making folders and started depending on searches which were very quick even with hundreds of thousands of messages my account had. Search can help you find and mark unread messages very quickly. This is mainly a note to self, but also for those of you who have similar problems with numerous unread messages: It gets slow when you have to mark way a hundred or more unread Gmail messages read, unless you know this quick search trick:
1. Enter “label:unread” without the quotes in the search field and click on “Search Mail”
You can also add labels for a desired ‘folder’ if you want to search only that group of messages, for example: “label:unread label:sent”. Whenever you type just “label:” in the search field a clickable list of available labels will appear below (this is how I discovered I had two different sent ‘folders’)
2. Click the check box above the messages (right from Archive buton) to select all messages on that page.
3. All the messages on this page of the search results will become checked, but right above the first message a new line will appear, stating: “All 20 conversations on this page are selected. Select all conversations that match this search”. Click on the underlined portion and you will have all the messages found in that search selected.
4. Click on “More Actions” drop-down button and select “Mark Read” and all of them are taken care of.
Warning: as always, if you’re not absolutely sure what you’re doing and whether those are really the messages you want marked read, don’t do this and skip to marking them read (or reading them all) individually.