Issue:
Outlook 2013 users are unable to connect to a mailbox present on an Exchange 2003 server and encounter the following error
Cause:
This is a by design issue .Outlook 2013 has been disallowed from connecting to Exchange 2003 (mailbox, public folders etc.)
Resolution:
Migrate the mailbox from Exchange 2003 > Exchange 2007 /2010.
Thanks & Regards
Rahul Thomas