So smtp check is the wrong way to verify an email address? Or the way im doing is wrong. Did i need to have SPF,DKIM config and send the real message to their S

So smtp check is the wrong way to verify an email address? Or the way im doing is wrong. Did i need to have SPF,DKIM config and send the real message to their SMTP server? My question is, is there any other way that this can be done? How do these services claim reliable validation in light of the above? I know that they are not going to reveal their methodologies, but can anyone on SO shed some more light?