[Dovecot] Failover authentication Ldap

Hi List

I use dovecot with LDA deliver, have quotas for my users use postfix as MTA server. as it could limit or refuse delivery of mail once the user has exceeded the limit of the quota?

As in my configuration could define multiple LDAP servers?

I have two servers with Active Directory, a PDC and a BDC, but I would specify both in the same configuration. for when the ldap server 1 has problems, authenticating against Ldap 2 .

Thanks

Michel