The Newsletter Plugin is not sending emails – Blocked by transient newsletter main engine

If you are using The Newsletter Plugin for WordPress you may run into a situation where:

1. Test email works fine
2. Test newsletter works fine
3. Real delivery is not working 🙁

After enabling the debugging mode in the plugin settings we have found the following

Blocked by transient newsletter main engine set 7585415 seconds ago by

After a quick search on the web we could not find any solution for that issue so we logged in to the database to check:

SELECT * FROM `wordpress`.`wp_options` WHERE `option_id` LIKE ‘%newsletter_main_engine%

We have found a record with a numeric value in it, setting it to 0 did not resolve our problem but after deleting this option our newsletter is sending out perfectly again!