Sorting by Sender IS NOT a sorting option! That is VASTLY incorrect. (I wanted to say a LIE.)

My "Conversation View" (you mean "Group By Conversation"?) is NEVER on. NEVER has or will be.
I have searched EVERY OPTION in settings, and there is NO WAY to filter by sender or subject anymore.
N O W H E R E. A T A L L.
LIARS.
You've just made my life that much more time consuming and difficult. You have no idea how infuriated I am at you dumbing down your email platform.

Some evil person sold you a bill of goods. You were an easy mark and they are laughing all the way to the bank.

This would deserve to be lampooned by Dilbert, if it were still out there.
Yahoo is now MUCH WORSE and LESS DESIRABLE than before.
Until you did this I would boast about Yahoo and how it was so much better than GMAIL, but NOOOOOOO! You just had to spend money on something that DIDN'T NEED TO BE FIXED!!!!!

If I could easily find and easily migrate all my emails to another provider you can be jolly sure I WOULD.
So the best I can now do is warn people to not use you any more than I would recommend AOL.COM.