As documented here:

http://answers.microsoft.com/en-us/office/forum/office_2013_release-outlook/how-do-i-disable-the-shadow-around-office-2013/75f2b52c-b6c5-4a2f-836d-044ae1bd4757

The MS Office 2013 shadow border bleeds through other applications, blinks and does not conform to the user's graphics settings.

How can it be disabled?

Hi,

As mentioned in the link above, disable the hardware graphics acceleration to check the result.

Also we can try start Office programs in Safe Mode to determine whether 3rd-party add-ins are the cause, in the Run dialog:

Type excel /safe and press Enter to start Excel 2013.

• Type outlook /safe and press Enter to start Outlook 2013.

• Type winword /safe and press Enter to start Word 2013.

• Type powerpnt /safe and press Enter to start PowerPoint 2013.

• Type mspub /safe and press Enter to start Publisher 2013.

• Type visio /safe and press Enter to start Visio 2013.

Disable the suspicious add-ins if there's no such issue in safe mode.

Please also update the graphics driver to check if this makes a difference.

Regards,

Melon Chen
TechNet Community Su

Typical Microsoft employee rubbish answer - zero relevance to the question... Just say you don't know!