Can't find anything in sent mail

Mail
1

if I go into sent mail and search for any word, the program finds nothing
if I go into the inbox and search for any word, the program returns the search correctly
why this? I’ve been using the program for a year without any problems
Thank you

2

Click the down-arrow in the search box and choose the folders where you want to search. Then start the search again.

3

thank you very much, works!