Check if email exist php

Question

I have a question, i have a php script to check if the email address exist.

But appear that yahoo, hotmail, aol and others providers are accepting any emails and not

Answer 1

The problem is gmail uses port 25 for their smtp outgoing mails, the other providers use different ports for their connection. Your response seems okay for gmail.com.

When you connect to gmail smtp it gives you response 250 2.1.5 OK j5si2542844pbs.271 - gsmtp

But when you connect to any other smtp who does not use port 25 it gives you null response.