After creating a return package you click on Send Package by Email:

After this you will receive the above mentioned error message.

Run a repair on Microsoft Outlook. Instructions on how to run a repair on Microsoft Outlook you will find below:

Outlook 2016

Open up the Control Panel on your PC (and show All Control Panel items, if necessary) and click on Programs, then Programs and Features.

1. Find Microsoft Office 2016 in the list and highlight it.(Selection also say Microsoft Office 365)
2. Click Change.
3. Select Quick Repair and Repair then follow the prompts.

 

Outlook 2013

Open up the Control Panel on your PC (and show All Control Panel items, if necessary) and click on Programs, then Programs and Features.

1. Find Microsoft Office 2013 in the list and highlight it.
2. Click Change.
3. Select Repair and Continue then follow the prompts.
4. After the repair is finished, please try the sync again.

For instructions on how to repair other versions of Microsoft Outlook please follow this article: https://www.companionlink.com/support/kb/Repair/Re-install_Outlook_2003,_2007,_2010,_2013,_2016. 

Microsoft Outlook is corrupt.