Hi Margaret, You can have Marketo support set up a sync filter that will block leads/contacts from syncing. I'd recommend doing a couple of things here. First, create a "Do Not Sync to Marketo" boolean field in SFDC on leads and contacts. Then, have a SFDC workflow that checks/unchecks this when your criteria is met. This will help when troubleshooting issues and help you in the future if you decide there is additional criteria to block other records from syncing. When you're ready to sync the records back to Marketo, uncheck the boolean field either manually or by workflow and during the next sync, that record will be pushed to Marketo. One issue that you will most likely run into are duplicates. Since you'll have leads in SFDC that are not in Marketo, if they're created in Marketo (maybe form fills, integrations, list uploads, etc), Marketo won't know that records already exist in SFDC and will create them as a new record in Marketo and sync it to SFDC, creating a duplicate. You'll need to set up a merging process to remove the duplicates, remembering to select the Marketo record as the master and ensuring the winning record does not have the "Do Not Sync to Marketo" field checked. Let me know if you have any other questions. - Kyle
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