[RESOLVED] Can't open Mailbox store in tasks and plans: A generic error of Microsoft Exchange Item Provider

When trying to create backup plan to backup exchange server 2010 SP2 Mailboxes we got the below error:

A generic error of Microsoft Exchange Item Provider

When viewing the details of the error we see:

MAPI IMsgStore has not been retrieved from IMAPISession

Solution:

Related to Acronis and Microsoft, we can found a fix with Exchange Rolup 4 for SP1. But we have SP2.
So to fix the issue:

We downloaded MFCMapi.exe.15.0.0.1039 on the exchange server to generate the error without using Acronis, and the error was:

Error:
Code: MAPI_E_FAILONEPROVIDER == 0x8004011D
Function CallOpenMsgStore( lpMAPISession, (ULONG_PTR)m_hWnd, lpEntryID, ulFlags, (LPMDB*) lppMAPIProp)
File MainDlg.cpp
Line 436

The error caused by missing public folder or un complete one.
So we have to force the MAPI client to ignore that check by editing the registry where the MAPI installed:

•Perform one of the following actions:

* If you are running a 32-bit version of Windows®, navigate to HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows Messaging Subsystem\CDO.

* If you are running a 64-bit version of Windows, navigate to HKEY_LOCAL_MACHINE\SOFTWARE\WOW6432Node\Microsoft\Windows Messaging Subsystem.

•If the CDO registry key does not exist, create a registry key that you name CDO.
•In the CDO registry key, if the DWORD value does not exist, create a DWORD value that you name Ignore No PF.
•Change the DWORD value to 1.
•Click OK.
•Close Registry and restart the server.
Recreate your plan and solved.