Ok, so you move OAB generation process from your old 2007 to new 2010 server. What if you stood up two 2010 multirole servers for HA, would you just create a new OAB on the second server and it automatically work?

No. Every organization only contains one mailbox server responsible for generating the Offline Address Book. This server is known as the OAB Generation server. The OAB Generation server then distributes the OAB to Client Access Servers for distribution to Outlook clients. Clint Boessen [MVP] http://clintboessen.blogspot.com/2011/01/exchange-2010-group-metrics.html Understanding Offline Address Books http://technet.microsoft.com/en-us/library/bb232155(EXCHG.140).aspx The Offline Address Book (Part 1 though 4) http://www.msexchange.org/articles_tutorials/exchange-server-2010/management-administration/offline-address-book-part1.htmlMCTS: Messaging | MCSE: S+M

No. Every organization only contains one mailbox server responsible for generating the Offline Address Book. This server is known as the OAB Generation server. The OAB Generation server then distributes the OAB to Client Access Servers for distribution to Outlook clients. Clint Boessen [MVP] http://clintboessen.blogspot.com/2011/01/exchange-2010-group-metrics.html Understanding Offline Address Books http://technet.microsoft.com/en-us/library/bb232155(EXCHG.140).aspx The Offline Address Book (Part 1 though 4) http://www.msexchange.org/articles_tutorials/exchange-server-2010/management-administration/offline-address-book-part1.html MCTS: Messaging | MCSE: S+M It is correct but only one modification: every organization only contains one Default Offline Address book. Actually we can have multiple offline address books be generated on multiple Exchange servers, especially in a mixed environment where both Exchange 2003 and Exchange 2007/2010 exist. Each OAB will update automatically and separately. Clients download OAB file based on the mailbox database configuration. To simply the OAB management and avoid any confusion, it is recommended to use one OAB. Best regards, Fiona LiaoPlease remember to click Mark as Answer on the post that helps you, and to click Unmark as Answer if a marked post does not actually answer your question. This can be beneficial to other community members reading the thread.