New Post: Issue Moving Inbox Folder

One of my users managed to move his inbox beneath his calendar (he does not know how, he did it on his iPhone) and we're unable to move it back. Every time we try it generates the following error:

Error: CopyFolder failed.
Code: MAPI_E_NO_ACCESS == 0x80070005
Function (null)
File MsgStoreDlg.cpp
Line 562

I created other folders beneath the calendar and I can move that folder so clearly it's something specific to the inbox folder.

Any thoughts?