[exim] using sasl2 db to check valid accounts with ACL...

Hello.

Using Cyrus and sasl for mailboxes and mail users, i would to prevent bounces
messages generated by Exim when a mail to an unexistant user arrive on my
mail server.
For that, i use the power of the exim ACL to reject those mails before they
arrive to the transport.
Today, i maintain a text file with, for each user, a line with the login.
I think it will be better if i use directly the user of the cyrus sasl db.

But, i don't know how to search in this db.

For example, bellow are the acl i use (in acl_smtp_rcpt):

accept      domains         = +local_domains
                endpass
                message         = Unknow user
                local_parts     = lsearch;CONFDIR/users/$domain         :\
                                  lsearch;CONFDIR/aliases/$domain       :\
                                  lsearch;CONFDIR/mailman_aliases

I would to replace the line " lsearch;CONFDIR/users/$domain" with someting
which search in the sasl2 db...

Thanks for your help,

--
E.Bullier