How to Suppress Blog Post Delivery
On the Edit Post screen, you'll see a box named Postmatic Delivery.
You can suppress blog post delivery by checking off the box next to Do not deliver this post via email. The box for this feature is unchecked by default. This is handy if you need to post about something but don't need to tell all of your subscribers about it.
We also have an option to disable new post notifications by default.
Go to Settings > Postmatic, then click on the Configure Posts tab.
In the Choose Posts to Deliver section, check off the box next to Do not send new posts unless I choose to.
Click on the Save Changes button and you're done - delivery of all blog posts will be disabled by default.
Within any blog post, you can always uncheck the Do not deliver this post via email checkbox before publishing to deliver a specific post.