Depending on what service you use for email, you can easily get this functionality back if you use this iOS email client app, instead.
Instead of waiting out Apple and the iOS software team to straighten out all of the issues with the iOS 10 Mail app,
If want to bring back all of the previous goodness about iOS Mail and get a few more bells and whistles, in the process.
If you are a Google Mail, Yahoo Mail or Microsoft Hotmail user, here is a almost exact replacement for iOS Mail that adds back all of the missing functionlities in iOS 10 Mail app and adds even more.
Look at this nearly exact email app replacement for iOS Mail.
I really like this email app a WHOLE LOT better than the stock Apple iOS Mail App while still looking very much like the standard iOS Mail App.
The most recent update adds a few more email services, so read the update details!
One user has successfully gotten this to work with their AOL account, if anyone is still using AOL.
This is a real beautiful email app to use and, if you are a large iPad Pro user, then this email app's UI really shines!
Email
Email - mail for Gmail Yahoo iCloud & Hotmail by Easilydo Inc.
https://appsto.re/us/wAla3.i
One of the real nice things about this app as it has a setting to allow the Safari web browser to open right up inside of this mail app.
Which is super convenient and quick!
If anyone can use this iOS Mail app replacement.
You're Welcome!
😉