Microsoft Exchange Server Error Code Look-up has been updated at the end of May. This tool is invaluable when it comes to knowing that a error 0x8000504 means something in plain English.

I STRONGLY suggest you download this one and keep it handy. You may find it here :

https://www.microsoft.com/downloads/details.aspx?familyid=be596899-7bb8-4208-b7fc-09e02a13696c&displaylang=en&tm

Happy hunting!