When running the Microsoft Exmerge utility, you may receive the following error in your exmerge.log file:
Error opening message store (MSEMS). Verify that the Microsoft Exchange Information Store service is running and that you have the correct permissions to log on. (0x8004011d)
Even though you may be a Domain Admin or Enterprise Admin, you will still receive this. In fact, you are at a distinct disadvantage being in either of these groups. In order to run Exmerge, you must have “Send As” and “Receive As” rights on the Exchange Mailbox Store that holds the given users mailbox. Domain Admins and Enterprise Admins have implicit DENY policies in this.
Resolution:
1. Open “System Manager”.
2. Drill down to the applicable Mailbox Store.
3. Right click on the store and go to “Properties”.
4. On the “Security” tab, add your user and ensure “Receive As” and “Send As” are allowed.
This should resolve the issue. The other consequences of this is that any user you add here will be granted FULL control of all mailboxes within this store. Use with caution.