> Dear all,
> 
> I would very much appreciate if anyone could help me identify the problem
> with several valid email addresses on my Listserv. Every time an email gets
> sent out, several addresses return an error stating: "The enclosed message,
> found in the --- mailbox and shown under the spool ID 6106 in the  system
> log, has been identified as  a possible delivery error notice for  the
> following  reason: "X-Report-Type:" field  found in  the mail header." An
> attached message reads, "This is a delivery status notification,
> automatically generated by MTA mailgateway1.slu.edu on Thu, 11 Aug 2005
> 20:29:32 -0500 Regarding recipient(s) : [log in to unmask] Delivery status :
> Failed. Message could not be delivered to the domain - slu.edu. Failed to
> accept the recipients. MTA Response :550."
> 
> I am told that this address and others are correct (including a few at
> AOL), so I wonder what the header might be contributing to having it
> rejected, and how I might change it. Thanks so much in advance.

Look closely at that attached message headers. You will see that the 
message was sent to the owner-listname@  or perhaps the special probe 
return-path. When mail is sent to these addresses, LISTSERV must consider 
them bounces. *IF* LISTSERV can understand the bounce, in other words can 
determine it is a permanent or temporary bounce, it will be processed 
automatically and disposed of. Of course this action is determined by the 
setting for Auto-Delete=.   As the manual states, bounces in which 
LISTSERV cannot understand are sent to the Errors-To= for examination for 
final disposition. In the case above, this is what happened.

To go a bit further on the above bounce, the MTA  mailgateway1.slu.edu is 
saying that it is unable to deliver mail for recipients  [log in to unmask] This 
of course is very vague, as many of these text responses are.  Since you 
have since determined that the recipients do in fact exist, then it is 
clear there were problems and/or misconfigurations at SLU when this 
message was received. If this continues, then you need to contact the 
admins at SLU with the evidence. BTW, it is NOT unusual to see a confirmed 
mail gateway reject all mail for the domain it is suppose to process mail 
for. 

Most of the time it just got misconfigured and other times they have 
multiple servers handling inbound mail and one or more have been 
misconfigured.