serach in new Yahoo
https://help.yahoo.com/kb/SLN36721.html
Find messages in New Yahoo Mail from a specific sender by searching the name of the sender, subject, content and refine the results to folders, date range, subject field, and more.
In the top search bar, click the Advanced Search Image of the Advanced search icon in Mail..
Enter your search criteria (result only show for the field you enter).
Optionally, limit by mailbox, date, attachment, photos or calendar invites.
From - enter an email address or username you received an email from.
To - enter an email address or username you sent an email to.
Subject - type a subject of an email.
Keyword - it will show up the emails containing your keyword.
Date - click the drop-down arrow Image of the Options icon in Calendar..
However Keyword search is missing. It was available 2 weeks ago for my account
Kamal V
shared this idea