Have you checked the web interface for list management on your host site?  It should show this info:

Full Description:
Reply-To= List|Sender|Both|None|net-address,[Respect|Ignore] 

Indicates whether the "Reply-to:" tag supplied by the sender of the mail file, if present, is to be preserved or discarded and, if discarded or omitted, what should be placed in the new "Reply-to:" generated by the server. The default value is "Reply-To= List,Respect". 

Note that some mailing systems are unable to process a "Reply-To:" field with multiple addresses correctly and may therefore disregard the Reply-to= Both option and treat it as Reply-to= List. 

WARNING: Setting this parameter guarantees only one thing * that LISTSERV will generate an appropriate RFC822 Reply-To: header in the mail it distributes to subscribers. There is unfortunately no guarantee that the mail transfer agent (MTA) or mail client on the receiving end will honor the Reply-To: header. This is because some mail clients, out-of-office robots, and Internet MTAs either simply do not recognize the existence of Reply-To: or do not implement it properly. Specifically, RFC2076 "Common Internet Message Headers" reports that the use of Reply-To: is "controversial", which is defined as: "The meaning and usage of this header is controversial, i.e. different implementors have chosen to implement the header in different ways. Because of this, such headers should be handled with caution and understanding of the different possible interpretations." (RFC2076, page 4). While L-Soft recognizes that it is sometimes important to provide an explicit Reply-To: header to indicate a response path, L-Soft cannot be held responsible for problems arising from the inability of a remote server to properly process Reply-To: headers. 

The two parameters are specified as follows: 

First parameter: List 
 Replies are directed to the list address. 
 
Sender 
 Replies are directed to the original sender. 
 
Both 
 Reply to both the original sender and to the list (see note regarding this above). 
 
None 
 No Reply-to: header is generated unless "Respect" is specified and a Reply-to: header is present in the original posting, in which case replies are directed to wherever the Reply-To: tag points. 
 
net-address 
 Replies are directed to the specified Internet address 
 


Second parameter: Respect     
 The original "Reply-to:" tag on the posting, if any, is kept. If no valid Reply-To: tag exists in the posting, the value defined in the first parameter of this keyword is used. 
 
Ignore 
 The original "Reply-to:" tag on the posting, if any, is ignored and discarded, and the value defined in the first parameter of this keyword is used instead. If Reply-To= None,Ignore, then a Reply-to: tag will never be sent by LISTSERV. 
 





>>> [log in to unmask] 12/30/2006 11:25:13 AM >>>
Hello, Everybody,

I wonder can I change Reply-To Prefix from the list to be absent frm the 
header?? Like Yahoogroups does have the feature that I am on a "bulletin 
board" announcement list that does not contains "Reply-To" field. I have 
in the list configuration as "List,Ignore". I would like to know if I 
can make "reply-to" to disappear?

Just wondering.

Thanks,
John :)