Duplicate Records, Same Email Address?

Hello,

I've searched and I can't tell if this exact issue has been addressed before.

I'd like Marketo to search the database for person records with a matching email address, and update the existing record instead of creating a new one.

We have a record that was created earlier this year with the source "Web service API":

I created a test form and submitted using the same email address and a new record was created instead of updating the existing one:

I re-submitted that form, and the activity was record on the new record. I created another Marketo form, submitted, and the new record recorded that activity as well.

Chat support tells me that a new person was created because the source is different. I understand that this is expected behavior if the new person is created by CRM sync. But what if the new person is created by a Marketo form fill? Is there a way to force Marketo to do a lookup on the email address field before deciding whether to create or update a record?

Thank you,

Chris

PS. We are using a custom built database, not Salesforce or similar CRMs.