Eudora (as well as, possibly, other e-mail clients) is susceptible to an 
exploit which can be used to conceal a fraudulent URL. In a fraudulent 
("phishing") spam I received this morning, the sender inserted a large 
number of character entities (in this case, spaces, coded as  ) into 
the middle of a URL to force the remainder off the right side of the 
status bar, hiding the true destination:

href="http://www.e-gold.com
 
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
          
@egegold.com/"> lang=EN-US 
style='mso-ansi-language:EN-US'>http://www.e-gold.com/alert 


When the mouse pointer is passed over the URL, the status bar at the 
bottom of the screen shows

http://www.egold.com 

and does not reveal the spoofed URL. One must view the message source to 
see the actual URL.

This technique is known to work on some browsers, but this is the first 
time I've seen it used to spoof e-mail clients.

I am told that if the URL gets much longer, recent versions of Eudora 
will overflow a buffer in a way that is exploitable by malware. This 
particular phishing expedition doesn't seem to take advantage of that 
vulnerability, hoever.

--Brett Glass