How to do a mass delete on iphone of my mail? Hide notifications?

It says I have 3497 unread emails. I've just tried to go through and mark them all as un-read on the computer but it hasn't changed anything.
Anyone have any ideas on how to hide the notifications, as it's annoying me a bit haha, thank you!

I think you've set up your phone to download your email using POP. If you set it up as IMAP and you have IMAP set up on your computer too then what you delete on your PC will mirror what you see on your phone and vice versa.
I would suggest deleting your mail accoutn on your phone and setting it up as IMAP.

hope that helps