Does iPhone download the entire email when we check for emails?

- Open iPhone mail app
- receive 10 emails
- open the email to read the contents
- get ‘loading’ icon..seems as if that’s when it’s trying to get the email
- the contents received in few seconds depending on the email
- move on to next email…and see the same loading icon

Is it that mail app downloads just the headers and the content is downloaded when you actually open that particular email? Ideally, I would like the email to be downloaded completely to my phone…this way I can quickly check my emails and move across the messages.

I believe Blackberry works differently where the entire email is downloaded and only attachment is downloaded when you try to access it.