> Managers here would really like it if, when you send 
> 
> To: List1, List2, List3, List4
> 
> 
> all the recipients could see which lists it was sent to, preferably via the
> To: subject header.

You want IETFHDR settings on the subscriptions. 

In the list header, to set it by default for future subscribers:

Default-Options= IETFHDR

To set it for any existing subscribers, send the command to LISTSERV:

QUIET SET listname IETFHDR FOR *@*


Since you mentioned in an earlier email that you wanted to use the 
Subject-tag, you probably also want to add this to your list header:

Misc-Options= IETF_SUBJECT_TAG

-- 
Francoise Becker

There is only one LISTSERV(R) -- the product that launched the 
email list communication industry in 1986. To discover the 
story behind LISTSERV, visit:
http://www.lsoft.com/corporate/20anniversary.asp