UniqueUri is not unique

I am trying to sync a local copy of emails from an exchange server. (O365)
I just noticed an email I received this morning has the same UniqueURI as a different email I downloaded yesterday.

Guess this is not the property to use.

What is the correct property to identify a message?
thanks

never mind, found the issue.id’s where identical with the exception of the case in one position.
needed to change collation settings for the column.

@gavinduffy,

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