Since change to Z-Push 2.3 I'm unable to read mails on Windows Phone 8.1 that are longer than Truncation Size allows during Sync. In opposite to iOS / Android Sync Applications the one on Windows Phone is using ItemOperations with BodyParts to request the complete Mail. In ZP 2.3.6 the SyncObject is faulty, furthermore Body Part Numbering is incorrect in WBXML. Additional Filters in HTML Content should be applied to first of all prevent some devices from crashing but on other hand helps to save data transmission volume. If these filters are really helpful in regards of performance in Outlook ActiveSync Connector should be investigated prior apply this part port the change set.
Affects Versions - sorry can only say I've fixed it and testing this fix now for the weekend on 2.3.6