Ipswitch IMail 7.04 and earlier stores a user's session ID in a URL, which could allow remote attackers to hijack sessions by obtaining the URL, e.g. via an HTML email that causes the Referrer to be sent to a URL under the attacker's control.
http://www.securityfocus.com/bid/3432
http://www.ipswitch.com/Support/IMail/news.html
http://online.securityfocus.com/archive/1/261096
http://archives.neohapsis.com/archives/bugtraq/2001-10/0082.html