Does anyone know where the flow/campaign for Unsubscribe lives? I've looked everywhere and can't find it and it says it is a "system flow action." Does this mean it's at the system level and cannot be modified - or reviewed?
If you mean the propagation of the system Unsubscribed value to other leads matched by email address, yes, that's an implicit system flow, not a user-facing flow in the UI.
Out of the box, marketo unsubscribe is a boolean field called "Unsubscribed".
Marketo's Durable Unsubscribe does this action. If that is the case it may be a duplicate email address entering your system. You can't really control the unsubscribe/de-duplication behavior unless you turn it off completely and build a custom system. You can create/track actions around this behavior as it registers as a "Change Data Value" for the "Unsubscribed" field. We have built in things such as "Unsubscribe date" and "Unsubscribed reason" to better assist with reporting and such.
We have an Email opt out field in Salesforce which is our unsubscribe on that end. I made the Email Opt Out field in Marketo as well, set up a smart campaign with a trigger of data value changes (Unsubscribe from False to True), then the Email Opt Out field is then changed to True.
I then have a nightly webhook that runs and pushes this data back to Salesforce.
If you want a reportable field, this would be an option even if you just need it on the Marketo side.
Hope this helps!
The default "email opt-out" field from SFDC is natively mapped with Marketo unsubscribed field if you are using the Marketo connector. You should not have to use a webhook to push that information.
We use a custom instance of Force.com (for Mortgage) with a custom integration which is why I use the webhook for that specific field to send data back to SF.
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