Delete old emails in gmail

1. First you need to look at the dates of those email, and then do a search based on date. Use this search string in the search box:
   
   before:2008-01-01
   
   and press Enter. 
2. After that, click on "Select: All" on the blue area above the first email in the list.
3. Then click on "All 20 conversations on this page are selected. Select all conversations that match this search".  at the top of the list of emails  Now press Delete.
 

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