[wplug] Email bounce problem

[Larry Daberko]

Bill Moran wrote:
> In response to Larry Daberko <larry at daberko.com>:
> 
> 
>>Hi,
>>	I wanted to see if anyone else had this experience and could tell me 
>>where to start looking.
>>
>>	I'm running a qmail server for my company and when a customer sends us 
>>an email, sometimes it bounces back and they see:
>>
>>
>>>From: postmaster at hosting.com [mailto:postmaster at hosting.com]
>>>Sent: Wednesday, June 14, 2006 11:28 AM
>>>To: user at customer.com
>>>Subject: Undeliverable Mail
>>>
>>>Unknown user: info at mycompany.com
>>>
>>>RCPT TO generated following response:
>>>550 <info at mycompany.com>... Relaying denied
>>>
>>>Original message follows. 
>>
> 
> 
> Yup.  Do you have any backup MXes configured in DNS?  If so, you need to
> ensure they all have updated mail address lists at all times.
> 
> It could also be on the user's end.  I've frequently had users complain
> that they couldn't send me email, only to find that they couldn't send
> email to _anyone_.
> 
No backup MXs are specified.  The customer's issue is intermittent. The 
customer uses a large webhost which uses another party's email servers. 
  This makes me believe one server in the round robin is misconfigured 
and there's a bunch of finger-pointing on their end.

Could anyone tell me what software would produce the type of error 
message?  Exchange or?

LBD