Microsoft Outlook Express allows remote attackers to monitor a user's email by creating a persistent browser link to the Outlook Express windows, aka the "Persistent Mail-Browser Link" vulnerability.
Buffer overflow in Microsoft Outlook and Outlook Express allows remote attackers to execute arbitrary commands via a long Date field in an email header, aka the "Malformed E-mail Header" vulnerability.
Outlook Express 5.01 and Internet Explorer 5.01 allow remote attackers to view a user's email messages via a script that accesses a variable that references subsequent email messages that are read by the client.
A Microsoft ActiveX control allows a remote attacker to execute a malicious cabinet file via an attachment and an embedded script in an HTML mail, aka the "Active Setup Control" vulnerability.
Microsoft HTML control as used in (1) Internet Explorer 5.0, (2) FrontPage Express, (3) Outlook Express 5, and (4) Eudora, and possibly others, allows remote malicious web site or HTML emails to cause a denial of service (100% CPU consumption) via large HTML form fields such as text inputs in a table cell.
Microsoft Outlook client allows remote attackers to cause a denial of service by sending multiple email messages with the same X-UIDL headers, which causes Outlook to hang.