How to check if a Email address exist or not using the command line

In this example we will test for the Email address [email protected], replace the gmail Email address with the email address you want to test

Open the command line/command promt and type in the following command

nslookup -type=mx gmail.com

This command will list the MX records of the gmail domain eg.

Server:        10.0.2.2
 
Address:    10.0.2.2#53

 
Non-authoritative answer:
 
gmail.com    mail exchanger = 5 gmail-smtp-in.l.google.com.
 
gmail.com    mail exchanger = 10 alt1.gmail-smtp-in.l.google.com.
 
gmail.com    mail exchanger = 20 alt2.gmail-smtp-in.l.google.com.
 
gmail.com    mail exchanger = 30 alt3.gmail-smtp-in.l.google.com.
 
gmail.com    mail exchanger = 40 alt4.gmail-smtp-in.l.google.com.
 
 
Authoritative answers can be found from:
 
alt1.gmail-smtp-in.l.google.com    internet address = 74.125.39.27
 
alt3.gmail-smtp-in.l.google.com    internet address = 74.125.65.27
 
alt4.gmail-smtp-in.l.google.com    internet address = 74.125.91.27
 
alt2.gmail-smtp-in.l.google.com    internet address = 209.85.225.27
 
gmail-smtp-in.l.google.com    internet address = 209.85.227.27

Select one of the servers listed in the list of MX records and pretend to send a message to that server from your local machine
- Connect to the server via telnet
```
telnet alt1.gmail-smtp-in.l.google.com 25
```
- Type in the HELO command
```
HELO
```
- Identify yourself using any email address eg. [email protected]
```
mail from:<[email protected]>
```
- Type in the email address that you wish to verify
```
rcpt to:<[email protected]>
```
After the last command entered, the server will respond with a message whether the email address exist/is valid or not e.g.
```
250 2.1.5 OK o15si4900954fal.31 //For success
```
and
```
The email account that you tried to reach does not exist. //Failure
```