how to delete email from iphone not from mail server

Most email now uses IMAP which mimics across all of your devices including your email server. For example, if you read the email on your phone, it will show as read on your PC. If you delete an email on your PC, it will delete on your phone and delete from the email server. You'll want to look for an email provider that can be configured with POP3. By using POP3 you each device is independent and you can have the email left on the server. However, just be aware that if you do that, if you delete an email on your phone, it will still be in your inbox on all other devices.

You will need to contact your provider to see if they support POP mail. If not, there isn't anything you can do. What is the reason that you wish to delete mail from the iPhone rather than sync it across all platforms? If mail on the phone is such a problem, then just remove the account and check the mail on a computer.

Hopefully soon IMAP will give us a option to not delete emails on mail server.

That will not happen. IMAP is working the way it is designed, so that mail resides on the server, an effort to keep mail together and to be able to access mail on multiple clients. As I said, it seems you shouldn't be using mail on the iPhone if it is causing you that much trouble. You can also consider consolidating your photos using iCloud photos and there is probably music on your phone that you haven't listened to in quite a while, if you have that much it is causing space issues. There are a number of other methods to reduce storage used, but if you are trying to delete mail, then it questions whether mail is necessary on the device.

mutlu1966 wrote:

Hopefully soon IMAP will give us a option to not delete emails on mail server.

That's not likely to happen. IMAP was developed precisely because of the problems managing email across multiple clients using POP.