We've added a new field to the Subscriber schema to help you track undeliverable subscribers!

The Subscriber schema now includes an undeliverability_date field, which records when a subscriber was marked as undeliverable. This is similar to the existing churn_date field, but specifically for tracking when email delivery to a subscriber fails permanently.

Additionally, you can now:

• Filter subscribers by undeliverability_date__start and undeliverability_date__end when listing subscribers
• Sort subscribers by undeliverability_date or undeliverability_date_desc via the ordering parameter

This change makes it easier to track when subscribers become undeliverable and manage your subscriber list more effectively.