During migration, Outlook repeatedly stops all activity with an Allow Access window and won't continue until you Allow for a max of 10 minutes at a time.
Every 10 minutes, this window will reappear and the migration administrator will need to keep allowing access to complete the migration.
This prompt will appear when an outside application, such as Notes Migrator, tries to access the Outlook address book and your anti-virus is either not installed or out of date. If you have anti-virus installed, the easiest fix is to update it. If you don't have anti-virus, follow the steps below.
Outlook has a Trust Center that allows you to disable the prompt. To get to this screen, open Outlook on each migration workstation, click on 'File - Options - Trust Center'
The setting to disable the prompt is in the Programmatic Access section.
Set it to "Never warn me about suspicious activity (not recommended)".