If you want to completely block certain deliveries and don't plan on sending them at a later moment, you can force MailerQ to return an error whenever such a delivery is attempted. The Forced Error functionality in MailerQ is often used by MTA administrators and deliverability managers to cancel individual problematic deliveries (for a certain ISP) or deliveries that were accidentally sent out. Deliveries blocked in this way will be removed and a custom error will be reported to the result queues and the logs. This can be specified based on a combination of sending IP or IP Pool, target domain, and tags (many-to-many labels, used for identifying individual or organized deliveries such as "campaign_X", "customer_Y" or "transactional"), either manually through the Management Console or programmatically through the REST API.
Image 1: Forced Errors in the Management Console
You can also add or remove Forced Errors and get a list of all Forced Errors using the REST API. This enables authorized external applications - such as third party deliverability monitoring tools or your own customer- facing platform - to cancel specific deliveries on the MTA level, even after the message has been queued. The most up-do-date documentation can be found here.
For questions and suggestions on the specific use case of Forced Errors, feel free to reach out to one of our experts via firstname.lastname@example.org.