Email changed in 3rd party connected database - dedupe?

I have a client that is doing some customization within their new Marketo database. They're sending lead records from a 3rd party database via Mulesoft integration. They want to make both the email and a lead ID (from the 3rd party database) the primary key in Marketo. The question is, if the email address changes in the 3rd party database, is there a way to ensure that Marketo will still dedupe if this change comes in, aside from looking for the duplicate ID field and manually merging?