Certified Mail Guarantees
When you use OnlineCertifiedMail.com, we guarantee that we'll put your letter in the mail within two (2) USPS business days. We also guarantee that the USPS will see and/or scan your letter so you'll know we've done our job (which is to get your letter to the USPS so that you don't have to).
With that said, the USPS doesn't guarantee anything with Certified Mail.
While they do successfully deliver a large number of certified letters, they aren't able to guarantee your letter(s) will be delivered in a certain number of days or at all, nor do they don't guarantee that a signature will be capture upon successful delivery.