single query for multiple table lookup based on third table

Hello,

Exim 4 integrated with MySQL 4.

I have four tables:

CREATE TABLE users (
uid bigint(10) unsigned DEFAULT '' NOT NULL auto_increment,
listemail varchar(200) DEFAULT '' NOT NULL ,
PRIMARY KEY (uid),
);

CREATE TABLE groups (
gid int(11) DEFAULT '' NOT NULL auto_increment,
listemail longtext ,
UNIQUE gid (gid),
);

CREATE TABLE mailalias (
mid int(11) DEFAULT '' NOT NULL auto_increment,
listemail longtext ,
UNIQUE mid (mid)
);

CREATE TABLE mailgroups (
id int(10) DEFAULT '' NOT NULL auto_increment,
uid int(11) ,
gid int(11) ,
mid int(11) DEFAULT '0' NOT NULL ,
PRIMARY KEY (id)
);

mailgroups contains relations between mailalias, users and groups:
select * from mailgroups;
+----+------+------+-----+
| id | uid | gid | mid |
+----+------+------+-----+
| 1 | NULL | 3 | 17 |
| 2 | NULL | 32 | 17 |
| 3 | 61 | NULL | 17 |
| 4 | 72 | NULL | 17 |
+----+------+------+-----+
What I need to do is:

Given mailalias.liste mail, get users.listemail and groups.listemai l
that are part of mailalias.liste mail. Ie: if mid is 17, find gid 3 and
32, uid 61 and 72. I found in the manual a way to do it with two
queries:

SELECT users.listemail FROM users,mailgroup s,mailalias WHERE
mailgroups.uid = users.uid AND mailgroups.mid = mailalias.mid AND
mailalias.liste mail
='$LISTEMAIL'

and then the same query with groups instead of users.

But because this is run within Exim, I need this in one query.
Basically, given an email address, I need to find the users and groups
that are associated with that address.

Any help would be appreciated.
Thanks
Kimo R.