MtaAuthHost in MTA configuration

[sn00p]

We've played with different types of configuration recently. What is a purpose of MtaAuthHost directive in MTA configuration?

We discovered that this parameter should be pointed to one of the store-server.

We have three store-servers now (store.domain1.my, store.domain2.my, store.domain3.my) and main MTA (smtp.domain.all) for startpoint for all users in different domains. The question is: to which store server should we point this main MTA? What would be wrong if this store fails? What kind of error we would receive if this store doesn't have necessary domain configured? Could we point main MTA to LDAP-server instead of store-server? Could we write all of three store-servers there?

It seems no logic for me to point this directive to one of the store servers instead of LDAP.

[sn00p]

Any help would be appreciated ))