I am trying to insert data into a custom object. My MD field with Contacts is Email__c. I want to use the email to identify the contact as is the unique identifier for my custom object. ( like when you insert in dataloader.io and for the contact id you select look via email).
Is it possible to do that on apex data loader? Whenever I try I get an error like Contact: id value of incorrect type: email@example.com
I have 100k records to insert into 60k Contacts. Replacing their email with SF contact's id will take alot of time