How add to address for mailing list semi-automatically?

[Frank Derichsweiler]

Hi List,

I am subscribed to some mailing lists. Every list has its own
(maildir) folder. Incomming messages are sorted by the delivery
agent. Further on I added all the addresses to the subscribe variable
(mutt 1.2). Therefore reply to the author of a message and replying to
the list works fine.
Now I would like to be abe to create a header with To:
<mailinglist-adress> by pressing e.g. M. Pressing m should produce a
template with empty To: field. Therefore setting a my_hdr in a
folder-hook is not appropriate for me.

How can I do that?

TIA
Frank