Push notifications are highly reliable compare to communication mediums like SMS, etc. The deliverability of HTTPS push notifications is high. The better the infrastructure of your push notification platform is, the more reliable it turns. 

The best web push notification service you can integrate with is Truepush. This free push tool is now adopted by more than 25,000+ brands globally. The features like RSS-to-push, audience segmentation, triggers, templates, project duplication, and makes this marketer’s favorite tool.