Symptom: You are converting to Google Apps, but you receive the error "This domain does not allow users to access the Email Migration API." You may also get "(403) Forbidden."

Cause: The migration API is disabled in your Google Apps Control Panel.

Solution: Please perform the following steps:

1. Open your Google Apps Control Panel.
2. Go to the "Advanced tools" page.
3. Scroll down to "User email uploads" (near the bottom.)
4. Check the box labeled "Allow users to upload mail using the Email Migration API."
5. Click "Save changes."