IOS 9.1 issue with Attachments

Hi,

several Iphones with IOS 9.1 are experiencing high data usage because Iphone automatically downloads full attachments regardless clients settings (not to load external images etc)

Zextras mobile settings are set to:

email text size : 6kb
HTML mesages: enabled
Html message size: 10kb

Attachments are always automatically downloaded regardless of size or type. Can you please advise how to stop automatic downloading of attachments?

Configuration:

Zimbra server:NE 8.6 patch 4
Zextras mobile 2.0.4

Regards