"Warning -2130574814 Count of processed mailboxes has exceeded the 90 percent limit." appears in the Mail Source Agent log (EMWMSA.LOG) after adding additional mailboxes to the Mailbox Synchronization collections and committing changes.
This is a license warning to let you know that you have exceeded 90% of mailbox licenses available.
This message can be safely ignored. The mailbox synchronization will continue, and newly added mailboxes will also be synchronized.
The license information is stored within the registry of the Migration Manager license server, which is the Migration Manager console by default.
Use Regedit to view the information in the following location: HKEY_LOCAL_MACHINE | Software | Aelita | Migration Manager for Exchange 2000/2003 | Counters | Exchange2x_InterOrgMailboxes. Each source server is displayed with the amount of licenses used by each.
Quest does not provide support for problems that arise from improper modification of the registry. The Windows registry contains information critical to your computer and applications. Make sure you back up the registry before modifying it. For more information on the Windows Registry Editor and how to back up and restore it, refer to Microsoft Article ID 256986 "Description of the Microsoft Windows registry": http://support.microsoft.com/default.aspx?kbid=256986