Same email address lives in Eloqua and Salesforce, but they previously did not have a sync setup.

We currently do not sync leads created prior to 2021 from Salesforce to Eloqua. This was done to limit the number of records in Eloqua during a data migration. However, we now want to start syncing all lead records to reduce duplicates. If the lead that lives in Salesforce has the same email as someone we already have in Eloqua (filled out a form, etc.), and then we allow the old lead to sync back, will they be automatically connected?