A simple solution is that send a test mail to that email address and if your message doesn't bounce, it is safe to assume that the address is real. But some web domains are including a new configuration to catch all email address meaning is that messages send to a address to a non-existent mailbox will not be returned to the sender but in most cases, such email messages will bounce.
How to validate a Email Address? - Answer is Ping
when a email is send, the message goes to an SMTP server which then looks for the Mail Exchange records of the email recipient's domain.
For Instance,When you send a email to xyz@gmail.com, the mail server will try to find the Mail Exchange records for the gmail.com domain. If the records exist, the next step would be to determine whether that email username (xyz in our example) is present or not.
Using a similar logic, we can verify an email address from the computer without actually sending a test message. Let say that we want to verify the address abc@gmail.com exists or not?
Step 1. Enable telnet in Windows. or if you have the PuTTY utility, skip this step.
Step 2. Open the command prompt and type the following command:
nslookup -type=mx gmail.com
This command will extract and list the MX (Mail Exchange) records of a domain as shown below. Replace gmail.com with the domain of the email address that you are trying to verify.
gmail.com MX preference= 10, mail exchanger = alt1.gmail-smtp-in.l.google.com
gmail.com MX preference= 20, mail exchanger = alt2.gmail-smtp-in.l.google.com
gmail.com MX preference= 30, mail exchanger = alt3.gmail-smtp-in.l.google.com
gmail.com MX preference= 40, mail exchanger = alt4.gmail-smtp-in.l.google.com
gmail.com MX preference= 5, mail exchanger = gmail-smtp-in.l.google.com
Step 3. It is not uncommon to have multiple MX records for a domain. Now pick any one of the servers mentioned in the MX records and "pretend" to send a test message to that server from you computer
For that go to command prompt window and type the following commands in the listed sequence:
3a) Connect to the mail server:
telnet gmail-smtp-in.l.google.com 25
3b) Say hello to the other server
HELLO
3c) Identify yourself with some fictitious email address
mail from:<dtcrunch@gmail.com>
3d) Type the recipient's email address that you are trying to verify
rcpt to:<abc@gmail.com>
The server response for 'rcpt to' command will give an idea whether an email address is valid or not. You'll get an "OK" if the address exists else a 550 error like:
* abc@gmail.com - The email account that you tried to reach doesn't exist.
* support@gmail.com - The email account that you tried to reach is disabled.
That's it! If the address is valid, you may perform reverse email search to find the person behind the address.