Message is not fully downloaded in Outlook Sync

Outlook Sync is an add-in to Outlook. Not only does it synchronize emails but also calendars, contacts, notes and other groupware. 

This article explains how to troubleshoot mail synchronization issues of big-size emails in Outlook Sync.

If you receive large emails with attachments, you may notice that they are not synchronized in full. When you click them, you see only headers. The reason is in the Threshold for full download (MB) setting of Outlook Sync. When Custom is selected, the value specified defines the size of emails that will be synchronized in full. However, to download the whole message, the entered value has to be bigger than the problematic message size. 

• To change the value, go to Outlook Sync tab > Settings > Advanced > Threshold for full download (MB). There is no recommended value for Threshold for full download (MB). It depends on the size of the messages that you usually receive. However, we do not recommend entering a value that is too big. The bigger the email, the more time and resources are needed to synchronize it.
• Check Apply threshold to already existing messages to synchronize all older messages as well.
• If you check Synchronize files in full-threshold mode, the custom value for full download will be ignored. However, if you do not want to limit the message size, we recommend selecting Full instead of Custom synchronization. In this case, all messages, regardless of their size, will be synchronized in full.