Microsoft
First published on TECHNET on Mar 07, 2007

Q: I’m logged onto a computer as the domain admin. I’ve tried running msextmzcfg tool using the mail account of the domain admin, but still show "unable to open mailbox" error message in the log file. Do i have to run the vbs permission script????
A: Domain user needs Full Mailbox Access and Send As rights to all mailbox. You need to run Grant Mailbox Permission script. Please refer "Configure permissions for Msextmz.exe" section in kb article http://support.microsoft.com/?kbid=930879