How To Delete Emails Permanently of iPhone 5?

Please can somebody help me?

I've been deleting all my emails but it still says in the settings that I have over 600MB worth of emails. Even when I've literally deleted them all.

HELP PLEASE as I'm low on space.

Have you deleted them from your trash folder? Thats where they go when you delete them from your inbox.

If its the same as my 6s, go into trash folder, click edit then it should give the option to delete all?

Thanks,

I've done all that.

There is absolutely nothing in ALL the mail folders

I just had a quick google, it looks like one way to do it is remove and re-add the email account from your phone?

Obviously youd need to know all the info/passwords etc to be able re-add it.

https://www.scrubly.com/blog/how-to-iphone/recover-email-storage-space-iphone/

is it account based settings? Can you login to apple.com on a computer and delete emails that way? (I'm not an apple user hence the lack of knowledge answer!)