[Mailman-Users] User unknown new error

[John Fleming]

This list used to work, and now it has a problem that I have found some 
threads about, but I still can't fix it - Not to mention, I don't know why 
it used to work and now it doesn't!  Here's the msg received back after 
trying to post to the list:

The original message was received at Sat, 23 Jul 2005 17:09:59 -0400
from vsat-148-64-5-87.c050.t7.mrt.starband.net [148.64.5.87]

   ----- The following addresses had permanent fatal errors -----
<orapormestre at impactoveneto.org>
    (reason: 550 <orapormestre at impactoveneto.org>: Recipient address 
rejected: User unknown in local recipient table)

   ----- Transcript of session follows -----
... while talking to wa9als.com.:
>>> DATA
<<< 550 <orapormestre at impactoveneto.org>: Recipient address rejected: User 
unknown in local recipient table
550 5.1.1 <orapormestre at impactoveneto.org>... User unknown
<<< 554 Error: no valid recipients

Is this an alias issue, and if so, how to fix?  Or permissions?  And why/how 
could it change without my input???  Many thanks!  - John