This is not a complete fix to the issue of Outlook 2013 always wanting to
test account settings on setup, but:

If you set the "your e-mail address" field to some other value, it will change
where the test message is sent without affecting any other settings (e.g.
login username).

This is useful in some use cases like, for instance, setting up an outlook
account just to convert an IMAP maildir to a PST file for use in a Windows
environment, when you don't want to spam the owners of those e-mail boxes with
test messages.