Niranjan_Kumbi_

Dan - Based on our investigation it doesn't appear like Lead IDs get reassigned by design. If at all you are seeing that behavior consistently, then it could be a bug occurring in certain flows (most likely a edge case). We would definitely want to gather steps to reproduce and address it -- a ticke...

Could you please point me to the support ticket?

Responding on behalf of Product team. Recognize the behavior is a bit confusing around the way master record is picked for email send. We'll investigate it internally to see if there needs an enhancement to bode well with SFDC sync updates. Is there a support ticket already?