How to migrate 200+ people company from hosting to Exchange 2010 in most non distruptive way

We want to implement Exchange 2010 in our organization which is spread over couple of locations. Right now we're using POP3/SMTP at hosting and all people are using Outlook 2007 and 2010. Mail for our company (and many more) is crucial form of communication with clients and internally.

Normally I would want to do it all in one day (and still I prefer that way) doing more or less this:

• setting up Exchange to work for company.com domain


• setup all the accounts mailboxes


• do any other related tasks (some testing etc.)


• switch MX records from old server to new server



• tell users (prepare instructions) to setup Outlook 2007/2010 with one of the following:
  
  
  
  
  • by modifying in Control Panel / Mail / New Account in same profile and leave the old mailbox for a few days and then remove the old mail server and just leave .PST files from it (or ask user to move the emails from PST to Exchange).
  
  
  • whatever option they wish :-)
  
  


• the list is just example for the sake of information

But the thing is our management would like to do it over couple of days/weeks since there will be problems with some people being offline, some people computers not working as they should, pick any other problem here (as we had experience with domain rename taking over 2 months for all people to finally switch to new domain).

So this starts tricky as after MX records change there will be no new emails in old mailboxes and people who will be offsite and will have problems with setting up Outlook to use Exchange will be out of order. Also with more then 200 people and few IT staff (most located in one location) this could cause some havoc with people who didn't read emails informing about change, who didn't proceed with instructions, who are offsite etc etc (we have all seen that during our domain rename instructions where last guys were migrated 2 months after rename).

So my plan would be (a bit complicated):

• inform users 1 month/1 week/1day prior to implementation


• make accounts/domains configured on Exchange and tell people even 1-2 weeks before change to add Exchange to their Outlooks.


• let exchange be able to send emails as company.com for the whole time before the final switch (so the emails would keep on coming to old mailbox but would let users to send emails from both just in case they make some mistake)


• make the final switch and tell users to only use Exchange and help them to migrate emails/remove old mailboxes.

Or

• inform users 1 month/1 week/1day prior to implementation


• make accounts/domains configured on Exchange and tell people even 1-2 weeks before change to add Exchange to their Outlooks.


• let exchange be able to send emails as company.com for the whole time before the final switch (so the emails would keep on coming to old mailbox but would let users to send emails from both just in case they make some mistake)


• go thru rooms of people / per project / etc and switch them one by one over days/weeks by implementing for each account on hosting Redirect to a separate domain company.com.pl which would be already set up and working so that all emails that come to people within room/project which have been migrated emails flowing to their mailboxes in hosting will be forwarded automatically to Exchange (by using 2nd domain).


• until all people are done that way MX would stay pointing to old server



• after all people are migrated switch MX and after a while switch redirection off

Additional option would be to use pop3 connector for everyone but this brings other problems:

• people's emails will be vanishing from their hosting Inbox and may cause some confusion


• there may be some race condition for Outlook's which download and delete emails after download (like mine)


• we would need to know all people's passwords for mailboxes

What do you think? Maybe there's other, better way? Or you have some nice idea how to better mitigate problems with migration.

Answer

I'd use a POP3 connector. Here's how I'd do it:

1. Setup the accepted domain as an Internal relay in Exchange. This will allow Exchange to deliver messages to itself when the mailbox exists and forward them when it doesn't.




2. Migrate users in batches. Reset their POP3 passwords to whatever suits you (because they won't need them after the migration). Create an Exchange mailbox for these users then setup the POP3 connector on the server (you could set it up in Outlook but I believe this adds unnecessary complexity). Migrate users 1 department at a time or 1 manageable batch at a time. After setting up their Exchange profile, import their PST back into Exchange. You may take as long as you want to do this as impact is minimal.




3. When all users have been migrated, change the domain type to authoritative and move the MX records to point to your anti-spam solution (Your appliance, or better yet, a cloud solution). Wait 48 hours then remove the POP3 connectors.