HT4810: iOS: Adding an email accountLearn about iOS: Adding an email account
Currently Being ModeratedJan 20, 2013 9:44 AM (in response to papito4)
Settings > Mail > Your Account > Advanced > Delete from Server > Never
With this settings your phone will download new mail an leave the original on the mail server. You can delete mail from your phone but it will remain on your server until you delete manually or have a different device delete it.
And if it's a POP account, it will never delate