substitution variables in ldap query_filter

I have a problem with a mail relay I inherited (I mention that because I'm 
kind of ignorant). I need to make it work so that mail to addresses like 
jheim <at> vulcan.math.wisc.edu work.

Right now, we use the canonical feature to rewrite the header. The problem 
is that as a result, the ldap lookup is never done. So then mail to invalid 
addresses like spock <at> vulcan.math.wisc.edu are rewritten as 
spock <at> math.wisc.edu and relayed on. That results in a bounce by the main 
server whereas I'd rather the ldap lookup gets done so the mail can be 
rejected by the relay.

I emailed my predecessor   about this and he suggested I get rid of the 
canonical rewrite and set up the ldap search to work for addresses like 
jheim <at> vulcan.math.wisc.edu.

Okay, so I re-read the ldap howto and i see that you can use other 
substitution variables besides %s. I'm thinking my query_filter could be
(mail=%u@%3.%2.%1)

But rather than poking and hoping and possibly breaking my mta in the mean 
time, I was hoping someone could direct me to some examples of use of these 
substitution variables.

--
John Heim
jheim <at> math.wisc.edu / 608-263-4189
"An operator of a vehicle shall stop the vehicle before approaching closer 
than 10 feet to a pedestrian who is using a service animal"
-- Wisconsin Statute 2005 Act 354,