Microsoft Exchange 2003 and Outlook Web Access (OWA), when configured to use NTLM authentication, does not properly reuse HTTP connections, which can cause OWA users to view mailboxes of other users when Kerberos has been disabled as an authentication method for IIS 6.0, e.g. when SharePoint Services 2.0 is installed.
https://oval.cisecurity.org/repository/search/definition/oval%3Aorg.mitre.oval%3Adef%3A477
https://exchange.xforce.ibmcloud.com/vulnerabilities/13869
https://docs.microsoft.com/en-us/security-updates/securitybulletins/2004/ms04-002
http://www.securityfocus.com/bid/9409
http://www.securityfocus.com/bid/9118
http://www.ntbugtraq.com/default.asp?pid=36&sid=1&A2=ind0311&L=ntbugtraq&F=P&S=&P=9281
http://www.microsoft.com/exchange/support/e2k3owa.asp