Ldap – pam_ldap, where is the filter set

A while ago I asked a question about this same issue already (Cyrus on CentOS with sasl / pam / ldap), and I came a bit further.
The Bind DN is no longer empty; LDAP works with all apps except imap.

Whenever I try to logon using imtest:

[root@testserv ~]# imtest -u my.Email@testserv.mydomain.com -a my.Email@testserv.mydomain.com

I get this message in slapd.log:

Oct 17 01:22:06 testserv slapd[1745]: conn=2627 op=2 SRCH base="o=mydomain,c=com" scope=2 deref=0 filter="(&(objectClass=posixAccount)(uid=my.Email@testserv.mydomain.com))" 

What I don't understand is, where does the filter "(&(objectClass=posixAccount)(uid=my.Email@testserv.mydomain.com)" come from?
I didn't put it in any of the config files; filter must be on mail, but whatever I change, this is what I get.

My /etc/pam.d/imap:

auth       sufficient   /lib64/security/pam_unix.so debug likeauth nullok
auth       sufficient   /lib64/security/pam_ldap.so debug use_first_pass
auth       required     /lib64/security/pam_deny.so
account    sufficient   /lib64/security/pam_unix.so
account    sufficient   /lib64/security/pam_ldap.so

My /etc/saslauthd.conf:

ldap_servers: ldap://127.0.0.1/
ldap_search_base: dc=%d,o=mydomain,c=com
ldap_bind_dn: cn=Manager,o=mydomain,c=com
ldap_password: ***********
ldap_auth_method: bind 
ldap_filter: (|(uid=%u)((&(mail=%u@%d)(accountStatus=active))) 
ldap_debug: 1 
ldap_version: 3

/etc/sysconfig/saslauthd:

# Directory in which to place saslauthd's listening socket, pid file, and so
# on.  This directory must already exist.
SOCKETDIR=/var/run/saslauthd

# Mechanism to use when checking passwords.  Run "saslauthd -v" to get a list
# of which mechanism your installation was compiled with the ablity to use.
MECH=pam

# Additional flags to pass to saslauthd on the command line.  See saslauthd(8)
# for the list of accepted flags.
FLAGS="-c -r -O /etc/saslauthd.conf"

Some values from /etc/imap.conf:

sasl_mech_list: PLAIN LOGIN
sasl_pwcheck_method: saslauthd

And in /etc/ldap.conf I set this:

# The user ID attribute (defaults to uid)
pam_login_attribute mail

As I said, other apps do work with LDAP, so I assume it's PAM/SASL related… and I'm stuck :-S