Hi
Gavin,
According
to your description, I would like to confirm the following information with
you:
1.
Which type of E-mail migration did you run? Staged Migration or IMAP migration?
2.
Are there any error messages when you tried to set up the third user's mailbox
in Outlook 2007 successfully? If yes, please provide us a screenshot about the
error message.
3.Did you ever run the Office 365 Desktop Setup on these computers?
Given to this situation, you can manually configure the Outlook by following the Method3
mentioned in this link for a temporary solution for this
issue.
For a further troubleshooting, I would like to suggest you re-test the Outlook Autodiscover and Outlook Anywhere at https://www.testexchangeconnectivity.comwith the third user's credential. if the test fail, please provide the detailed error message or screenshots that include the detailed error message.
If
there are any questions, please feel free to post.
Thanks,
Jolin Qiao
Jolin Qiao