On Mon, 10 Apr 2006 16:08:15 EDT, "Gartner, James" said:

> The unknown user errors are strange:
> SOFTBOUNCE [log in to unmask] 5.0.0 550 5.1.1 <[log in to unmask]>... User unknown 
> SOFTBOUNCE [log in to unmask] 5.0.0 550 5.1.1 <[log in to unmask]>... User unknown

The 5.0.0 is an "unspecified" error, and Listserv is probably erring on
the side of caution - if the box at the other end is confused regarding
the nature of the error, it may well decide there isn't an error when you
retry. ;)

> BOUNCE [log in to unmask] 5.1.1 Mailer mail02.COLOHFA.ORG said: "550
> 5.1.1 User unknown" 

RFC3463 is pretty specific about 5.1.1 however:

      X.1.1   Bad destination mailbox address

         The mailbox specified in the address does not exist.  For
         Internet mail names, this means the address portion to the left
         of the "@" sign is invalid.  This code is only useful for
         permanent failures.

(Note that your 2 softbounces contain 5.1.1, but in a *later* field. It's
the 5.0.0 that matters....)