User blog comment:CrazyAwesomeGamerGirl/Question about Email/@comment-24886041-20150214210813/@comment-24886041-20150224194416

Ah; "platform" means OS X, Windows, iOS, etc. You've answered that bit in that you're using the default Mail app on iOS.

If you go into the Settings app and select "Mail, Contacts, Calendars", you'll get a list of accounts. If you select an account and tap on the account name, then click on Advanced, you can check the details. If you have "IMAP Path Prefix" on one line, then you're using IMAP.

You will also note on the screen where you tapped on the account name, there's an "archive messages" option at the bottom that states "save deleted messages in your All Mail folder". This means that if you delete a message, it saves it on the mail server and just removes it locally.

Conversely, if you save a message locally (outside your inbox), it is copied out of the IMAP folder, but if you don't move files around and delete via the web interface or from another device, it will delete from your local device the next time it connects to the server. I have a number of gmail, ISP and iCloud addresses scattered between a number of webmail accounts, iOS devices and desktop computers, and this is always the case for me.