Filters in LeadConduit can be tricky, especially when you're working with both Enhancements and Deliveries in your flow. The following are a few use cases to guide you.
When using an enhancement (e.g. Phone or Email validation) you typically don't want to reject a lead when the service cannot return a definitive judgment. Instead, you only want to fail leads when the outcome is definitive.
Considering this, a Filter that stops only explicit failures is the way to go:
Deliveries are different from Enhancements because this is where you send the data out of LeadConduit. If the outcome of this step is anything other than a Success, your lead data wasn't accepted at the destination, whether that's your CRM, Marketing Automation System, Call Center, or another delivery endpoint.
Placing a filter directly after a delivery ensures the final disposition of the lead is accurately recorded, allowing you to easily use reporting dashboards to note total successes, failures, and errors in a flow or to a destination.
Considering this, a Filter that stops anything other than an explicit success is the way to go:
You'll notice in the Delivery example, the filter sets the Outcome of the lead to the Outcome of the Delivery Step. This means if the delivery step returns an Error, the Lead Outcome will also be an Error.
While these are Recommended Best Practices, there are sure to be exceptions from time to time. If you are ever in doubt, please reach out to Support and we'll be happy to advise you on your specific scenario.