Based on the limited amount of information you provided, the possible answers you may receive are a bit restricted. One wild guess I will offer you is: the destination system, which responded with the "invalid character" rejection message, is using some form of spam-defense that is non-compliant with the applicable RFC, and is improperly declaring the asterisk unacceptable in an email address. You'll get better responses here if you present more detail about where the error message came from. It may also be useful if you contact directly the administrator of the system that produced the error. In the context of a LISTSERV(tm) Daily Error Monitoring Report, which is my best guess for where you found the snippet of info in your message, you might set the NORENEW subscription option for the affected subscriber, if you want them to remain a member of the list. But it would be better overall for them to find a new email provider. >>> [log in to unmask] 12/7/2006 6:54:44 PM >>> Hello, everybody! I wonder what does that means? I never heard of. Last error: 5.5.2 501 #5.1.3 Invalid character ('*') in > username. Can you explain this for me? Thanks, John :)