Question:
Is it possible to assign a lead owner during a list import?
Answer:
No. The reason for this is because lead ownership is a Salesforce functionality and should be first done from within Salesforce. If you are not able to do the assignment in Salesforce, here is one option that is available to you within Marketo:
1) Upload your leads into Marketo's Lead Database without lead owner information. i.e. your import CSV will not have any lead owner column in it. More information on importing leads can be found here: Import a List of Leads from a Spreadsheet into Marketo (Import List).
2) Once the list import is successfully completed and your leads are in Marketo, you can use the "Sync Person to SFDC" flow action to assign lead ownership. More information on the "Sync Person to SFDC" flow action at Sync Person to SFDC.
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