I have only had the Droid Turbo 2 about a month. Previously had Droid Maxx. Battery life was much better on Maxx, although I was told this one would be better still. Maxx displayed entire email message, occasionally prompting to download pictures. Turbo 2 prompts you to "View Details", and then to "View Entire Message", each of which requires a separate download, as does "Show Pictures"
Is there any setting that would load the message all at once?
Go into your settings for your email account>Data usage>Download Size and select 'All'.
I got my T2 the day it was released and it seemed like a long couple of days getting everything set to my liking, so I don't remember if there was something else I found to get my full email messages to show up. I also recommend deselecting the 'only on wi-fi' settings, but that's just my preference.