Hi,
Sep 10 11:27:00 localhost dovecot: auth: pam(testuser1,127.0.0.1): pam_authenticate() failed: Permission denied Sep 10 11:27:00 localhost dovecot: auth: ldap(testuser1,127.0.0.1): invalid credentials
I am not clear from this if you are using pam auth first and ldap auth 2nd, or if you are trying to use pam to do your ldap authentication for you. Assuming the former, I would guess that you are either failing the auth_bind, or the attributes you are using for user_filter/pass_filter aren't matching the username format. I would start by checking the settings in your dovecot-ldap.conf file...
Sep 10 11:27:02 localhost dovecot: auth: Debug: client out: FAIL#0111#011user=testuser1
So, I don't know what permission is being denied by PAM, or if that was there or not when this did work. I can access my LDAP server just fine.
What else can I check?