We've noticed a problems with Iphone with Zimbra - 8.0.7_GA_6021.

The iOS of iPhone 5S - iOS 7.1.2 (11D257), but the problems occurred at previous versions of iOS also.
We've noticed, that the messages which have above ~ 400 kb, and more, are shown correctly in Iphone. All the mails which have below ~ 400 kb are empty inside on Iphone. Is there any relationship between the messages size of ~ 400 kb, and the correctness of emails viewing?

Thanks for any suggestions.