download headers only

With the iPhone's Mail client, the entire message is not downloaded with new messages. The message header is downloaded and your chosen number of message preview lines with the iPhone's Mail client. The rest of the message body is not downloaded until a message is opened and depending on your internet connection at the time, attachments must be selected to be downloaded.

Hello.

You didn't answer my first question when you performed this test.

When connected via wi-fi or your carrier's cellular network?

And regarding 'while on the move', this makes no difference to U.S. residents since the data plan required by AT&T with the iPhone is an unlimited data plan - truly unlimited.

And it is funny that is usually takes longer to open a message when I'm connected to AT&T's cellular network than than when connected via wi-fi - the time to wrap the text and images to display should take the same amount of time regardless my internet connection. And when I'm connected to AT&T's cellular network, if I receive a message with a photo as an attachment that is over a certain size, or a number of photo attachments that combined are over a certain size, I must select the attachment or attachments one by one for the attachments to download and open. When I'm connected via wi-fi I don't have to do the same.

Wow - I just tested the same thing - and you are completely right - the Mail App must indeed download the entire message - despite setting the Preview Pref to Headers only - thus the data trafic is the same no matter what mode you use.

This is a somewhat undocumented "feature" that is not welcome when you want push enabled but are looking to limit data traffic (here in NZ data is the killer cost).

Looks like another Apple feature request for something assumed to be in the Phone in the first place.
Like the lack of letter count in the Text App for instance.

I'm interested in knowing your test results. I see different behavior when connected via wi-fi than when connected via AT&T's cellular network in regards to photo attachments appearing inline or viewed in place automatically when connected via wi-fi, but not always when connected via the cellular network. With a large photo attachment - over 3MB that I received recently, I had to select the attachment in the message body to download the attachment in order to view the photo when connected via wi-fi, so it isn't always consistent, but I'm fairly certain the attachment would not have downloaded automatically when connected to the cellular network if it didn't when connected to a wi-fi network.

In regards to the Mail client being smart enough, the YouTube app will stream better quality for a selected video when connected via wi-fi than when connected via the cellular network, so hopefully it is the same with the Mail client.

I'm very surprised if using Push alone downloads the whole message. Push is provider dependent and most of the providers I know only send header information to speed up the process. You may want to check with your mail provider to see how much they are pushing out. Obviously, your phone will receive whatever is being sent to it.

However, you are right that the whole message is downloaded to the Mailbox regardless of the Preview setting. I use Fetch but set preview to None, send myself a long message from my PC and when the Mail indicator on my iPhone showed it had arrived, switched to Airplane mode like you did. I then opened the e-mail and the whole message was there.

I guess Apple have set this up for use with data-inclusive packages like AT&T in the US and O2 in the UK. This is convenient if you then have to switch to Airplane mode as you can still check your messages but I agree it could be expensive if you receive a lot of mail and have to pay for data (although e-mails are pretty small and I think that there is a size limit before you need to choose to download more and attachments don't download automatically).

In Settings, Mail Contact Calendars, under Mail, Preview, select None.

"So disabling preview will download headers alone?"

Try it and see.

When connected via wi-fi or your carrier's cellular network?

And while on the move where - when roaming internationally?