We are migrating from Ex2003 to Ex2010. Right now we have about half our mailboxes on each. On our 2010 server, I noticed that there are two Offline Address Books listed in EMC: 1. "Default Offline Address List" on "EXCHANGE2003-SVR" with "Default OAB = True" and "Distribution = Public Folders" 2. "Exchange 2010 OAB" on "EXCHANGE2010-SVR" with "Default OAB = False" and "Distribution = Web-based; Public Folders." My primary question is: Is it safe to right-click on the 2010 OAB and set it as "Default." When I do so, I get an info box that says: "Are you sure you want to set "Exchange 2010 OAB" as the default offline address book for all new mailbox databases? This is confusing to me, because what I think I want to do is set it as the default for all *existing* mail databases as well as *new* databases. If this is not the way to do it, could someone tell me how to change the default OAB for existing databases? Also, the reason I am researching this is because we are seeing a ton of "Sync Issues" in our Outlook 2010 clients. Much of what I have read indicates the errors we are seeing may be related to problems downloading the OAB. I am hoping that by changing the default OAB from 2003/PF-based to 2010/web-based, we will see these issues abate. Does this sound reasonable? Thanks

You shouldn't change the OAB at this point. Have you not replicated the system folders to the Exchange 2010 server? That is the primary cause for the errors that you are seeing. OAB changes should be something that is done as part of the Exchange 2003 removal process, not midway through. Simon.Simon Butler, Exchange MVP Blog | Exchange Resources | In the UK? Hire Me.

Thanks Simon, glad I asked! Frankly, I'm not sure if system folders are being replicated. I suspect not. We used a consultant to set up our 2010 servers and subsequently found that while the public folder hierarchy was visible to users on Exchange 2010, they could not open the folders and read the content, if htat makes any sense. So we've been going through ESM on the 2003 server, right-clicking each public folder, choosing the replication tab, and adding the 2010 server as an object under "Replicate content to these public stores." However, I have found no reliable method to verify that a PF on 2003 has been truly replicated to 2010. Microsoft PSS suggested I run a cmdlet and compare the bytes of the folders. Haven't quite got around to that. Anyway, I will look into how to replicate the system folders. The first article I fould simply said to do so from the 2003 EMS console -- but I am not seeing exactly where to do that. I'll post back when I find it. Thanks again.

To replicate the system folders is the same method - but you need to be in the System folders view in ESM. Right click on Public Folders and choose View System Folders. As for confirmation replication, item count. get-publicfolderstatistics on the Exchange 2010 server, compared with the items in ESM. The system folders (OAB, Free/Busy) should not be 0. Simon.Simon Butler, Exchange MVP Blog | Exchange Resources | In the UK? Hire Me.