Top tip: Converting from Exchange On-Premise to Office 365

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Written by Thomas Speekenbrink

Overview:

Customers running the Exchange Online Synchronizer version and who will convert from Exchange On-Premise to Office 365 will get duplicates as soon as the Synchronizer will be linked to the Office 365 environment.

Why does this happen?

Tips:

After the conversion to Office 365, the userstore_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 duplicates.

Unfortunately we cannot offer a conversion tool for this, because we can't predict the new userstore id's in a Office 365 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