Java EE (Java Enterprise Edition) General Discussion

I'm currently using JavaMail to read emails from a server using POP3 and am getting a Messaging Exception - Error getting UIDL when I try to retrieve the UIDL for a message. This code has been in production for a few years on different client sites and has just started getting this exception for a particular email for one of the clients. The code that retrieves the UIDL is:

com.sun.mail.pop3.POP3Folder pf = (com.sun.mail.pop3.POP3Folder)folder;
sMsgID = pf.getUID(msg);

Does anyone know why this exception would be occurring?

Thanks for your help.