Lately I've seen a lot of questions regarding the use of homeMDB in policy filters. I want to use this post to explain the reason that ExBPA warns about this, and hopefully clear up the confusion a...
Updated Jul 01, 2019
Version 2.0
Blog Post
Hi Christian,
HomeMDB and certain other attributes are linked values so that their corresponding backlink values can be automatically generated by the AD. That is, HomeMDB is a linked value so that HomeMDBBL on the mailbox stores can be calculated automatically by the AD and reflect all the users who point to that store. It's similar to the type of relationship that exists between the Member and MemberOf attributes, except for homeMDB it's a one-to-many relationship instead of many-to-many. This is in contrast to other DN-valued attributes such as HomeMTA. If you look at the MTA object which is referred to by a HomeMTA attribute, you'll notice that there's no backlink for all the users that point to it, because HomeMTA is not a linked value.
From a replication standpoint, there's no real benefit to having a single-valued linked attribute replicated via LVR. It's just that the design of LVR is such that the AD does not distinguish between single-valued and multi-valued linked attributes. They are all replicated by the same mechanism.
HomeMDB and certain other attributes are linked values so that their corresponding backlink values can be automatically generated by the AD. That is, HomeMDB is a linked value so that HomeMDBBL on the mailbox stores can be calculated automatically by the AD and reflect all the users who point to that store. It's similar to the type of relationship that exists between the Member and MemberOf attributes, except for homeMDB it's a one-to-many relationship instead of many-to-many. This is in contrast to other DN-valued attributes such as HomeMTA. If you look at the MTA object which is referred to by a HomeMTA attribute, you'll notice that there's no backlink for all the users that point to it, because HomeMTA is not a linked value.
From a replication standpoint, there's no real benefit to having a single-valued linked attribute replicated via LVR. It's just that the design of LVR is such that the AD does not distinguish between single-valued and multi-valued linked attributes. They are all replicated by the same mechanism.