When Your Email Grows to Over 1000k Unread!!!!

Try these steps.....

Gmail
How to mark all unread emails as read in Gmail
1: When logged-in to your Gmail account, in the search box up top, type the following, then press the search button: is:unread

2: Click the down-arrow in the "select" button, then choose "all."

3: The emails on the page you're on should now be checked; however, to select all of your unread emails, you need to click where it says "Select all conversations that match this search." It will be centered, just above the top-most email, as pictured below:

4: Finally, click the "More" button, then click "Mark as read."
5: Done!

YAHOO

How to mark all unread emails as read in Yahoo!

1: When logged-in to your Yahoo! email account, right-click on "Inbox" in the left-hand sidebar, then select "Mark All Read."

2: That's it! To note, the box below might show if you have a ton of emails that it has to mark as new.

Hotmail

How to mark all unread emails as read in Hotmail

1: When logged-in to Hotmail, right-click on "Inbox" in the left-hand sidebar, then select "Mark all as read."

Source: http://www.zdnet.com/blog/btl/how-to-mark-all-unread-emails-as-read-in-gmail-and-more/80754