Please explain auth error in auth.log

Hi all,
verifying my auth.log I found this entries:

Feb 4 09:32:56 mmnucs saslauthd[1097]: pam_unix(smtp:auth): check pass; user unknown
Feb 4 09:32:56 mmnucs saslauthd[1097]: pam_unix(smtp:auth): authentication failure; logname= uid=0 euid=0 tty= ruser= rhost=
Feb 4 09:32:56 mmnucs PAM-univentionmailcyrus[1097]: continuing as user usera
Feb 4 09:32:56 mmnucs saslauthd[1097]: pam_ldap: error trying to bind as user “uid=usera,cn=users,dc=IBMMN,dc=local” (Invalid credentials)
Feb 4 09:32:56 mmnucs saslauthd[1097]: pam_krb5(smtp:auth): authentication failure; logname=usera uid=0 euid=0 tty= ruser= rhost=
Feb 4 09:32:58 mmnucs saslauthd[1097]: DEBUG: auth_pam: pam_authenticate failed: Authentication failure
Feb 4 09:32:58 mmnucs saslauthd[1097]: : auth failure: [user=usera@mmn-ing.de] [service=smtp] [realm=mmn-ing.de] [mech=pam] [reason=PAM auth error]
Feb 4 09:33:10 mmnucs saslauthd[1097]: pam_unix(smtp:auth): check pass; user unknown
Feb 4 09:33:10 mmnucs saslauthd[1097]: pam_unix(smtp:auth): authentication failure; logname= uid=0 euid=0 tty= ruser= rhost=
Feb 4 09:33:10 mmnucs PAM-univentionmailcyrus[1097]: No or ambigous result, found 0 entries.
Feb 4 09:33:10 mmnucs PAM-univentionmailcyrus[1097]: failed to map username
Feb 4 09:33:10 mmnucs saslauthd[1097]: pam_krb5(smtp:auth): authentication failure; logname=usera uid=0 euid=0 tty= ruser= rhost=
Feb 4 09:33:12 mmnucs saslauthd[1097]: DEBUG: auth_pam: pam_authenticate failed: User not known to the underlying authentication module
Feb 4 09:33:12 mmnucs saslauthd[1097]: : auth failure: [user=usera] [service=smtp] [realm=] [mech=pam] [reason=PAM auth error]
Feb 4 09:34:35 mmnucs saslauthd[1097]: nss_ldap: reconnecting to LDAP server…
Feb 4 09:34:35 mmnucs saslauthd[1097]: nss_ldap: reconnected to LDAP server ldap://mmnucs.IBMMN.local:7389 after 1 attempt
Feb 4 09:34:35 mmnucs saslauthd[1097]: pam_unix(smtp:auth): authentication failure; logname= uid=0 euid=0 tty= ruser= rhost= user=mmiklaw
Feb 4 09:34:35 mmnucs PAM-univentionmailcyrus[1097]: No or ambigous result, found 0 entries.
Feb 4 09:34:35 mmnucs PAM-univentionmailcyrus[1097]: failed to map username
Someone here to answer me following questions:

  • Why the pam-modul “PAM-univentionmailcyrus” is used even though Cyrus is not installed at all?
  • Why it continues with existing usera?
  • How to prevent this behavior further?

Thanks