Is it possible to migrate Exchange 2003 content from an old domain "sub.olddomain.local" to Exchange 2010 in a new domain "domain.local" without losing information, if I want to do a clean install of the new domain without co-existence and cross-forest/site-migration? The reason is, that the old domain is faulty, because my predecessor screwed up the active directory.

It's a small company with only 15 users, so it wouldn't be too much work to create the new users, groups and permissions, but I am a little bit worried about the Exchange part.

I'm planing to export mails, calendars and contacts to PST files (is there an advantage of using EXMERGE instead of an Outlook client to do the export?) on the old Exchange 2003 server and import them to the new users in the new domain (Exchange 2010). The users will keep the same external email addresses as before, but I suspect that this is not enough for exchange to regognize that it is the same user.

How will this affect existing mails, calendar items, address items and public folders? What additonal steps are necessary to allow users to work seamlessly with the old items?

What will happen to appointments? Will exchange be able to allocate the new users to the old user items as long as the email adress of the new user is the same or how do I reconnect the old and new accounts in a way that participants of an appointment are correctly identified and handled?

I read that users won't be able to reply to old emails. How can I fix this?

  • We did this for a company last month. The details on why are a little hazy, but we had to use Outlook for the transfer. There weren't any extra steps to get users working with the old items. It wasn't possible for them to reply to old emails, and there's no fix to that AFIAK. – Chris Ting Oct 22 '11 at 11:12
  • From my research I did so far you have to add X500 proxy addresses, but I'm not sure if this is enough and how exactly it works. Another keyword for that problem is "LegacyExchangeDN". As far as I understand you have to build the X500 proxy addresses based on the "LeagacyExchangeDN" of your old domain. I hope someone can explain this in more detail and tell us if this is enough if we have to go that route of migration. – JPS Oct 22 '11 at 11:26

Migrating from one Exchange organization to another is relatively straight forward and people do it every day. If the old mailboxes are less than 2GB in size you can export them using Exmerge. If they're larger than 2GB you'll have to export them from Outlook due to the 2GB file size limit of Exmerge (old ANSI format versus new Unicode format).

External to internal emails will work exactly as they did before and new internal to internal emails will work exactly as they did before. The only issue you'll run in to is when internal users reply to emails that were sent in the old system. Outlook uses the LegacyExchangeDN attribute when replying to emails and since your new user objects will not have the LegacyExchangeDN attribute from the old system they'll get NDR's when replying to old emails. They fix for this is to add the old LegacyExchangeDN attribute to each new user object as an X.500 address.

  • Will adding the X500 address solve all possible problems (calendars, appointments, participants of appointments) and the end result will be the same as a "normal" migration using co-exitence? – JPS Oct 22 '11 at 13:44
  • The X.500 address will deal with the LegacyExchangeDN so that replies to emails from the original system will be delivered to the new mailbox. As for the rest of it, it's been awhile since I've migrated to a new Exchange server so my suggestion would be to test it with 1 2 accounts and see what other issues crop up. Create a Calendar appointment for 1 user in the old system and add the 2nd user as an attendee. Set up both users in the new system and export their mailboxes from the old system and import them into the new system and see what happens to the Calendar appointment. Continued... – joeqwerty Oct 22 '11 at 16:06
  • The appointment will import into the new Calendar but I'm not sure what will heppen with the attendee. – joeqwerty Oct 22 '11 at 16:07

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