In reality, blacklists don't have the power to block messages as widely as people think, and most recipients only reference them during rigorous spam-filtering. Many blacklists are implemented more like flags, with most users taking listings with a grain of salt, and delisting is often automatic after a short time. The influence and reputation of the blacklist can affect how long it remains listed, but even then, just because an IP is listed now doesn't mean it was always that way or will be in the future. To confirm if an issue exists, recipients should pass a note to Postmark support team, which can help assess deliverability trends and investigate potential causes of any affected messages.