Why can't I sign up with a temporary email?

 If you have registered on sites like Facebook or Instagram, you have probably encountered a situation where your email is not accepted or a confirmation email with a code is not sent to you. This is a result of a hidden security algorithm that blocks your registration as undesirable.

There can be many reasons for this to happen, and here are the main ones:

1. Public domains. When you create a temporary email with a public domain, no one can guarantee that it is not already on the blacklist of the particular service you are trying to register for