I have been having some problems with some old designs that were working as address books on 5.0.11 but have not been working since we upgraded to 6.5.1.
The error message we were getting was
Directory Assistance database has one or more invalid replicas for domain xxx
We had several custom address books and one of them was working fine.
I looked at the design of the databases and have come up with the following details
For the address book to work properly the following views needed to be in the database.
($PeopleGroupsByLang)
($PeopleGroupsCorpHier)
($PeopleGroupsFlat)
($PeopleGroupsHier)
($Resources)
($Rooms)
($Users)
Make sure that your design included the version of these views from the most recent copy of the pubnames.ntf as there has been some additions to the ($Users) view.
For mail routing to work properly you need to make sure your field names correspond with the names used by Domino.
I am only using the custom address books for mail routing so I am sorry I do not have any information on what is required for authentication.
I hope this information is of use in answering some of the questions that have been posted and if anyone finds any inaccuracies or additional information on this subject please post it for others to use.
Duncan Caldwell