Microsoft has created a fix for this security issue for Outlook

This is a special alert message to registered users of Microsoft Office, Microsoft Outlook 98, Microsoft Internet Explorer version 4.0 or later, and Microsoft Windows 98.   We want to inform you of a security issue that affects e-mail packages including Microsoft Outlook 98 and Microsoft Outlook Express versions 4.0 or later.  Microsoft has created a fix for this security issue, which can be downloaded from http://www.microsoft.com/security/

This security issue involves how e-mail software handles file attachments with extremely long file names.  When users attempt to download, open or launch a file attachment that has a name containing more than a certain number of characters, their action can cause the program to shut down unexpectedly.  It is possible - although difficult - for a hacker to cause malicious code to be executed on a computer as a result of this problem. However, this cannot be caused accidentally, and to date we have received no reports of users being affected.  More information on this issue can be found at http://www.microsoft.com/security/bulletins/ms98-008.asp

Microsoft takes security very seriously, and we know you do as well.  Microsoft is committed to ensuring that all its customers enjoy a rich, safe and secure computing experience and developers have been working around the clock to isolate and deal with these issues.  Microsoft has provided software patches for both Outlook Express and Outlook 98 at http://www.microsoft.com/security/ We strongly recommend that you download the appropriate patch immediately.

To ensure customer safety with regard to this and other security-related issues, Microsoft is investigating further to uncover variants that the current patch may not block. Microsoft will communicate additional information about this research as it becomes available.  You can also visit http://www.microsoft.com/security/. for the latest information and updates, and to register for the Microsoft Security Notification Service.