My guess: When you get an email, the app just downloads the header (from, subject, time, etc) not the entire message. Once you actually open it, the message is downloaded.

So if you hadn't opened the email on your phone, it wouldn't have been accessible while on call unless WiFi was connected.

 

You can't be on call and use data at the same time. It's a disadvantage of using cdma network.

edit: sorry typo

 

FTFY

You cache a certain amount of information on the phone including emails. This information is accessible when you are on a phone call. Also if you are on Wifi you can use data.

 

well, in his case it didn't cache

 

The default caching is 4 days of synced mail.

I pushed mine up to 30 days to avoid this exact scenario.

I've got 8gb internal, might as well put it to use.