iOS9 continuing email problems

I upgraded to iOS9 on my iPhone 4S and have been having problems with email every since. I bought my 4S the month they came out, 4 years ago. I noticed the first day with iOS9 I had old emails in my POP email account. I get 30-40 emails a day and I always deal with them and delete them within a day or two. These same emails get downloaded to my Mac Pro and deleted off the server on a daily basis. On my iPhone with iOS9, looking at my POP account, I noticed a boat-load of old emails which had been previously deleted. I know these emails aren't on the server, so they weren't downloaded after the upgrade. They don't exist anywhere except my iPhone. I scrolled back through the emails until I got to May, 2015, and the scroll bar was maybe 1/10th of the way down the screen. Is that indicating that every email that's ever existed on this iPhone since I bought it in October, 4 years ago is still on this iPhone???

Ok, so there's a boat-load of emails, and now I see there's a Trash All option when I hit Edit. The Trash All button didn't do anything. While it looked like my emails were gone, I'd put the iPhone down for 5 minutes and they'd all be right back. I deleted my POP account and recreated it. All of the trashed emails came right back. I read that for some reason another email account could be the culprit, so I deleted all 4 of my email accounts, 1 POP and 3 IMAPs. I then recreated them using the settings used for those same accounts on my iPad which is not running iOS9. Gosh, golly, gee, all the ****** old email came right back into my POP account! So, I started deleting them 100 at a time. I'd tap Edit, then select 100 emails, and then tap Delete. The little "busy" indicator next to my wi-fi signal would rotate for 6 minutes. I'd select the next 100 and repeat the process. The next morning, I noticed a message on my iPhone telling me that it couldn't delete the emails, and they were all back.

I'm now at a point where I delete 4 at a time and they successfully go into the trash and I am able to delete them from the trash. This process takes about 2 seconds. But, overall, how fricking long is that process going to take to delete them all? There are thousands of emails in there to be deleted!

BTW, I've also noticed that I'm not able to delete emails out of one of my IMAP accounts. When I try, the email disappears, and then after a couple minutes I get an error saying that the email couldn't be deleted. I have to go to my old iPad to delete those.

Needless to say, I'm not happy. I've been having problems with Yosemite since I downloaded and installed it last fall, and now iOS is a huge problem. I'm beginning to wonder if Microsoft is writing these OSs because they are clearly not up to the former Apple standard.

Any suggestions? And, pleased don't tell me to reset my iPhone. I don't want to go through setting up all of those apps again.