Error Access Denied when migrating a mailbox
To resolve this issue referr to the NetIQ Exchange Migrator User Guide to ensure that you have the appropriate permissions set. Removed the source mailboxes contact from the group and then try the migration again.
The NetIQ Exchange Migrator User Guide is located in the below directory.
<instalation directroy>\NetIQ\Exchange Migrator\Documentation
This error can because by not having the appropriate permissions over the mailboxes that you are migrating. We have also seen the "Access Denied" error be caused by the contact(s) in the target organization for the source mailboxes being member of group(s).