Today at work I had to check if the email of a client exists. Using the method below you can get this information directly from the mail server responsible. In this example I am querying my SMTP server at work (the domain is obviously fake, but the replies are legit).

1. check if any MX record exists

# host -t MX mail is handled by 10

2. connect to the SMTP server

# telnet 25
Connected to

3. greet the email server

250 at your service

4. define where you’re sending the email from (don’t forget < and >)

mail from: <[email protected]>
250 sender <[email protected]> ok

5. define who you’re sending the email to

rcpt to: <[email protected]>
550 #5.1.0 Address rejected.
rcpt to: <[email protected]>
250 recipient <[email protected]> ok

6. quit

221 See ya in cyberspace


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