I've run into a few instances in which we have a flow step set up if leads are sent an email, add to SFDC Campaign with status = sent. We then see new leads (of existing contacts) are created in salesforce because they have been added to a SFDC campaign. Why is it creating multiple leads (for some not all ). Do new leads get created if they get added to a SFDC campaign through Marketo?
Obvious question, but do they have the same email address? If yes, then is the Contact already in Marketo? If the Contact isn't in Marketo,
then even though it is in SFDC, Marketo won't know to merge the lead it has in Marketo with the SFDC contact, thus it will create a new record.
Well the smartlist is taken from Salesforce. I tried to find differences, but it was the same email address. We were able to compare it to the already existing contact that way.
What you describe cannot exist as is. If a contact in SFDC is synced to Marketo and you add the corresponding Marketo lead to an SFDC campaign with an "add to SFDC campaign" flow step, it will NEVER create a new lead in SFDC.
What you describe will happen in various specific situations:
(1) to understand how an SFDC contact could not be synced with Marketo, look here: "Sync with Marketo" mysteries part 1