This question already has an answer here:
Suppose I want to delete all emails older than year 2012 in gmail. Currently, what I do is put
Before: 2012 in the search box. However using this method, I have to delete the emails 100 conversations at a time. This is time-consuming and tiring on my finger muscles. How can I delete all emails older than year 2012 in gmail in one stroke?
EDIT: The answer in the possible duplicate no longer works. I am no longer able to select all conversations. Emails have to be selected and deleted 100 conversations at a time.