ActiveSync shows e-mail in plaintext instead of HTML

Hi all,
Since a few days I have running Zimbra 8.0.4 OSE and the Zextra Suite (1.8.7). I have a LG Nexus 4 and my partner HTC Sensation XE. Syncing (over https) is working flawlessly.
We use the native e-mail app with JellyBean 4.x. All our mail is in plain text with URL-links for the images! I want the e-mail(s) in HTML. I thought I made a wrong configuration but I can't find any option to enable/disable plaintext/HTML.
I also tried an evaluation with Zimbra Network 8 version and then I receive the (synced) e-mails in HTML with the option to show the images on my Nexus 4.

So there's a difference between the ActiveSync of Zimbra Network edition and the module ox ZxMobile. Or is there an hidden option to enable receive the e-mails in HTML?

TIA