The mailing list for listmasters using Sympa

[address@concealed]

Is there a way to create a scenari where a subscriber (lets say address@concealed) 
may send to a list via alternate address searched in LDAP (lets say 
address@concealed)?

I was thinking something along the lines of:

altaddress.ldap:
  host ldap.foo.org
  port 389
  suffix ou=people, dc=foo, dc=org
  scope sub
  filter (|(altaddress=[sender])(mail=[sender]))

send.altaddress:
  title  restricted to subscribers with alternate addresses

  is_subscriber([listname],[sender])   smtp,mime,md5  -> do_it
  search(altaddress.ldap,[sender])     smtp,mime,md5  -> do_it


...but wouldn't this allow ANYONE to "send" who has an "altaddress" attribute?
(an LDAP entry could be returned who is not a subscriber of the list)

How do I associate 'address@concealed' ([sender]) with 'address@concealed' (the 
subscriber)?
It would be fairly easy if I could chain tests together like:

search(altaddress.ldap,[sender] smtp ->
       is_subscriber([listname],[sender]) smtp  -> do_it

...is that possible?

Help.
I know alternate addresses are possible in Sympa, but I can't figure how to 
do it...even the simplest ancient Majordomo software can support subscribers 
with alternate addresses (and not send the e-mail multiple times)....

thanks in advance for any assistance.

---
Dave Le Blanc