Hello: Does Exchange 2010 SP1 still use X500/LegacyExchangeDN addresses for internal e-mails? Does it matter if the client is Outlook 2003, 2007, or 2010? We've acquired a company, I'll call them SS Corp, and will create new mailboxes for them in our forest. If I copy their old LegacyExchangeDN addresses over to X500 proxy addresses on their respective new mailboxes, will the following work: 1.) Replies to old e-mails between SS Corp employees. 2.) Updating old meetings between SS Corp employees. Will the SS Corp attendee names resolve correctly to show their new mailboxes' free/busy times? 3.) For calendar reservations accepted by Auto Accept, will Auto Accept allow updates from the new user? I plan to copy the calendar entries from their old conference rooms over to new conference rooms. Does Auto Accept use the X500 address to check if the user is allowed to update the meeting? 4.) For the questions above, does using a specific version of Outlook help? I've read the article at http://blogs.technet.com/b/sbs/archive/2009/05/21/cannot-reply-to-old-emails-or-modify-old-calendar-items-after-pst-mail-migration.aspx and other similar articles. I plan to test some of this, but my testing environment is very limited. In Exchange 2003, I know that #1 works. My question is specific to the behavior with Exchange 2010 SP1. Thanks.

Yes Outlook and Exchange still use x500 addresses for 2010 SP1, doesn't matter the version of outlook. 1. Yes but you don't need to create the x500 addresses the cross forest mailbox move will bring over the legacyexchangedn automatically. 2. Yes 3. Yes, no issue. It's not really " is Auto Accept using x500 addresses", it's really outlook that's using the x500 address and Exchange needing to be able to resolve it. If it can't then whether or auto accept will work or not is a moot point. If you're planning on moving all mailboxes from SS corp forest to your forest in one botch then you really don't have to worry about these iissues. Now if you need to do a coexistence phase over a few weeks then that's a bit trickier ie. cross forest free busy setup to include contacts, GALsync etc.James Chong MCITP | EA | EMA; MCSE | M+, S+ Security+, Project+, ITIL msexchangetips.blogspot.com

I would consider recreating all the meetings - or at least test things out. 2 and 3 probably will break. Since you are creating new mailboxes and not moving mailboxes and copying the meetings from another org to yours, I think you'll find that retaining the old glue between users and their respective meetings isnt going to work so well.

I'm following up on my own post to bring closure to it. I didn't use any type of migration utility or cross-forest mailbox move. I simply exported the LegacyExchangeDNs of the old Exchange mailboxes and then added them as X500 proxy addresses to their respective new mailboxes. Does Exchange 2010 SP1 still use X500/LegacyExchangeDN addresses for internal e-mails? > From my testing, yes. Does it matter if the client is Outlook 2003, 2007, or 2010? > From my testing, no. We've acquired a company, I'll call them SS Corp, and will create new mailboxes for them in our forest. If I copy their old LegacyExchangeDN addresses over to X500 proxy addresses on their respective new mailboxes, will the following work: 1.) Replies to old e-mails between SS Corp employees. > Yes, this will work. Replies will go to the mailbox with the X500 proxy that's the same as the old LegacyExchangeDN. 2.) Updating old meetings between SS Corp employees. Will the SS Corp attendee names resolve correctly to show their new mailboxes' free/busy times? > Yes, this appears to work from my limited testing. I didn't have enough time to do more thorough testing. 3.) For calendar reservations accepted by Auto Accept, will Auto Accept allow updates from the new user? I plan to copy the calendar entries from their old conference rooms over to new conference rooms. Does Auto Accept use the X500 address to check if the user is allowed to update the meeting? > Yes, this appears to work from my limited testing. I didn't have enough time to do more thorough testing. 4.) For the questions above, does using a specific version of Outlook help? > From my testing with OL 2003, 2007, and 2010, they all seem to behave the same regarding X500 proxy addresses.