Q: Why did IOS 10 take away the Trash All email option??

Did you ever find an answer?  I've been searching online and can't find the reason or how to bring it back.

Not everyone, just some people.

And those of us smart enough to do it on their Mac where it is easier.

Have you found a solution?  Unlike csound1 I don't carry my mac in my pocked.  When I do get home deleting them on my mac doesn't remove them from my phone.

Then you must not be using an IMAP account, I don't carry my Mac in my pocket either.

Sick temp fix.  Delete email program then reinstall from iTunes.  The whole thing takes about 15 seconds.  Mail accounts don't need to be reset up.  Quicker than checking each one off 1 at a time.

I have Fios, hotmail etc.