Q: We have 90K+ user mailboxes over different time zone. We want client rebase their own mailbox first with the Outlook rebasing tool and SMS push quiet mode.Then rebase rest mailbox. Do you think there is a lot of email flow because of same time rebasing?
A: Yes, the rebasing (regardless of Exchange or Outlook) will send updated requests to meeting recipients. That will generate some traffic but in fact, the Outlook tool will likely be spread out over more time - so it will be continual traffic over a longer period vs. a blast of updates if the Exchange server-side is run.
Either way the traffic shouldn't be too dramatic.... But I would recommend communicating to your user base that they will see new updates to meeting invites and that they should accept them, etc. They'll also see an increase of Out of Office Messages that will appear as a result of the resend. We have some sample communications out on our website if you'd like to leverage those (we used them in our internal release). Visit http://www.microsoft.com/dst2007 and click on MSIT Deployment Guidance on the right hand side.