Can’t delete email.

Try going into Settings > Accounts & Password > account > Account > Advanced > Deleted Mailbox, and under On The Server tap the 'Trash' folder so that it gets a tick against it - then come out of that series of popups by tapping on the relevant buttons at the top of them and see if you can now delete emails.

I do not have a hotmail account and it wasn't spam. However, thanks to chatting online with an apple customer service rep, they recommended that I uninstall the mail app (this thought would have never crossed my mind for some reason). They wanted me to re-install it and then re-set-up my mail accounts in Settings. Well, I did uninstall the Mail app, but then, I downloaded the AOL mail app, since that is who my carrier is now (was verizon but got moved over, although still has the verizon.net ending). After using AOL app for a week and remembering how much I hated it, I re-downloaded and installed the Mail app and everything has been working fine ever since. Those troublesome emails that were in deleted/undeleted limboland never re-appeared. So, problem solved.

Thanks, I had an email that would not load, to view it, nor would it stay deleted, just returning after next opening the app. After deleting the Mail app and then re-downloading it, I needed to login to the account and also turn it on again in Settings>iCloud>Mail. This has solved the problem and the email has not come back.

The solution posted did not work for me as there was no "account" Account option after I clicked on "Accounts & Password". I am assuming they were changed in an update.

After messing with this for over an hour, I discovered that when I clicked an option (I apologize, I can't remember which one exactly- might have been the curving arrow for forwarding or printing) on one of the offending emails, there was a "see other options" or "see related items" link that isn't normally there, and didn't show on other emails. When I clicked that link it gave me an "available threads" screen and the email was listed as a "thread". I have no idea how or why. However, once I selected it there and clicked the trashcan icon, it deleted and allowed me to delete the other few random emails that previously kept coming back. I hope this helps.

Did you uninstall the Mail app itself? I also deleted all of my mail accounts in the settings area but it didn't solve the problem. I believe what solved my problem was getting rid of the Mail app for more than a few days

I have had the same problem for longer than one year. It is not an issue related to all mail. It is specifically related to spam mail. You can delete, but immediately the pop up says unable to delete. This occurs on iPhone, iPad, MacBook Pro, and Cloud. It seems to act more like a permanent invitation to spammers. I have tried too many hundreds of times as my inbox fills. At present there are about 20 / 50 emails I cannot delete or move. I have even deleted the old email addresses from accounts and devices.

ADD : All of the mail that has this problem, for me, seems to be a Hotmail account also. Those accounts no longer exist.

ARRRGH! No, sorry, they are back again. I just wanna cry. I have been trying to delete the same emails for almost an entire year now.

I’ve spoken with support. Deleted all mail and accounts. Terminated email accounts. Changed all app accounts to new email addresses. Still getting undeleteable Mail.