This issue occurs due to being on Exchange Server 2003 and the administrator running the Microsoft Dynamics CRM E-mail Router does not have access to the mailbox.
This issue was resolved with Microsoft Dynamics CRM 2011 Update Rollup 11. Once Update Rollup 11 has been applied, a registry key must be enabled:
1. Go to Start, click Run, and type regedit
2. Navigate to HKEY_Local_Machine\Software\Microsoft\MSCRM Email
3. Set the value of the ExchangeAdminAccountName
property to the SAMAccountName property of the Exchange Admin Account on the computer that has the Rule Deployment Wizard installed.
for other considerations.