Issue
You want to use a list import to change the Lead Owner/Sales Owner information in Marketo.
Solution
It is not possible to update Lead Owner information via list import. The Lead/Sales Owner fields in Marketo are system managed and can only be updated via the CRM or by a Change Owner flow step. If you wish to update this information, you will need to do so in your CRM and let the info sync back down to Marketo, or create a Smart Campaign with a Member of List filter and a Change Owner flow step.
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