Eudora 4.x allows remote attackers to bypass the user warning for executable attachments such as .exe, .com, and .bat by using a .lnk file that refers to the attachment, aka "Stealth Attachment."
https://euvd.enisa.europa.eu/vulnerability/EUVD-2000-0341
http://www.securityfocus.com/bid/1157
http://www.peacefire.org/security/stealthattach/explanation.html
http://news.cnet.com/news/0-1005-200-1773077.html?tag=st.ne.fd.lthd.1005-200-1773077