Converting from Exchange On-Premise to Office 365

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When running the Exchange Online Synchronizer and converting users from Exchange On-Premise to Office 365 here are two tips to help you prevent extra work afterward.

  1. Having more than 50 users, use ranks.
  2. Prevent duplicates entries as soon as the user(s) will be linked to the Office 365 environment.


Ad 1) When you use Office 365 with a lot of users it could be that you experience throttling issues from time to time. In the articles Throttling in Office 365 we explain why and how to solve this by defining ranks in the Exchange Online Synchronizer.

Ad 2) After the conversion to O365, the mailstore_id's will be changed and the users cannot be matched anymore. You will have to re-link the users. This will delete all Synchronization history and thus create duplicate entries.

Unfortunately, we cannot offer a conversion tool for this, because we can't predict the new userstore id's in an O365 environment.

To avoid duplicates the Outlook Calendar, contacts and tasks need to be cleaned. 
See this article on how to do this: Clean the Outlook calendar