SMTP Error from my server?

[Chris Maness]

Jay Chandler wrote:
> Chris Maness wrote:
>> I have not seen this error before.  What does it mean?  (I will 
>> change the actual e-mail to protect the address from spam bots).
>>
>> To: NOSPAMtim at adelphia.net
>>> From: Mail Administrator <Postmaster@<PostmasterDomain>>
>>> Subject: Mail System Error - Returned Mail
>>> Date: Mon, 17 Sep 2007 14:48:17 -0400
>>>
>>> This Message was undeliverable due to the following reason:
>>>
>>> Your message was not delivered because the return address was refused.
>>>
>>> The return address was "<NOSPAMtim at adelphia.net>"
>>>
>>> Please reply to Postmaster@<PostmasterDomain>
>>> if you feel this message to be in error.
>>
>> Chris Maness
>> Sys Admin
>
> Looks to me like a failed sender verification callout-- these are 
> generally construed to be abusive.  I can't easily tell from your 
> munging whether it's your server or Adelphia that's doing it, though.
>
This is the only e-mail address that I am having this problem with, and 
it has been going on for a year or so now.  What other info would you 
guys need to tell what it is.  I guess I don't understand the whole 
"sender verification callout"  I'll have to do a little google to find out.

Thanks,
Chris Maness
Sys Admin for a couple of tiny domains.