[Mailman-Users] Bounces to single user, but only from mailman

[John Swartzentruber]

There is a user on one of my mailing lists that bounces all of the 
mailing list messages. This started less than a week ago.

First question: is it possible to see the actual bounce messages before 
the user's subscription is disabled? When mailman notified me that his 
address was disabled, it included the bounce message that caused it, but 
before then, I couldn't figure out how to see it. I found the bounces in 
my sendmail (maillog) log and my mailman log, but not the actual message.

The strange thing is that I can personally send him messages to the same 
address and from the exact same server (this is just a personal server 
that I have). Stuff only bounces when it comes through mailman.

Here is the data from the bounce message:

>   ----- Transcript of session follows -----
>... while talking to mail.sysnet.net.:
>  
>
>>>>>>> MAIL From:<heap-bounces+xxxxxxxx=sysnet.net at hihd.org> SIZE=2293
>>>>        
>>>>
><<< 553 Requested action not taken: mailbox name not allowed or chunk too large
>501 5.6.0 Data format error
>  
>
>  
>

I looked in the FAQ and archives for "chunk too large" but didn't find 
anything. A larger google turned up some similar reports but no 
suggested solutions.

Now, this user sends me this: "My sysadmin tells me that mailman is not 
issuing a "mail" command when contacting sysnet so mail from the 
listserv is bouncing."

What does this mean? I'm not a big sysadmin, I just have a small 
email/webserver that I use for personal use. I'm reasonably familiar and 
competent with Linux, but am not an expert. Can anyone provide me some 
answers or clues? My guess is that his ISP is screwed up and they're not 
talking sense, but I'd like some confirmation before telling him that.

I'm running Mailman 2.1.4, RedHat 9, and Sendmail. Thanks in advance for 
any help.