Apply Retention Tags Prior to Migration

Is there a way, either natively or using third party tools, to "pre-tag" emails residing in Exchange on-prem, PRIOR to migrating the emails into Office 365?

So for instance, if we ran a search for any emails which have the words "dog and cat" and wanted to apply a personal retention tag of 7 years to those items.  Then, when we migrate those items to Office 365, they will have already been tagged to be retained for 7 years.

John