Most Internet users consider the process of sending emails is very easy and involves only the sender sending the email and the receiver receiving it. But in reality emails work in a more complex manner than assumed by many. Any sort of discrepancy between the interacting servers will lead to mail bounce. A major reason being, invalid email addresses of recipients.
This blog post will cover how to check whether an email address is valid or not. But before that let’s just briefly know the working principle of emails to make sure where a sent email can go wrong. At first the mail sent by the sender goes to an outgoing mail server using SMTP (Simple Mail Transfer Protocol). They sort the emails they receive and send it to the DNS (Domain Name System) server. The domain is noted and now the SMTP has the required information about the domain. It then sends the mail to the target domain’s MTA (Mail transfer Agent). It then decides where exactly to send the mail, i.e. to the receiver’s inbox.
Follow the steps to check whether an email id exists or not. Let’s verify the validity of the email address firstname.lastname@example.org
- Enable telnet in Windows
- In Command Prompt from your computer, type the following command:
nslookup – type=mx gmail.com
This command will extract and list the MX records of a domain. Note the MX records for gmail.com listed below:
gmail.com MX preference=30, exchanger = alt3.gmail-smtp-in.l.google.com
gmail.com MX preference=20, exchanger = alt2.gmail-smtp-in.l.google.com
gmail.com MX preference=5, exchanger = gmail-smtp-in.l.google.com (lowest preference no.)
gmail.com MX preference=10, exchanger = alt1.gmail-smtp-in.l.google.com
gmail.com MX preference=40, exchanger = alt4.gmail-smtp-in.l.google.com
Replace gmail.com with the domain of the email address that you wish to verify.
- It is normal to have multiple MX records for a domain. Select any one of the servers, preferably the one with lowest preference level number.
- Pretend to send a text message to that server from your computer. You can do this by the following way:
- Go to Command Prompt Window
- Type the following commands in the given listed sequence:
- Connect to the mail server: telnet gmail-smtp-in.l.google.com 25
- Say ‘hello’ to the other server: HELLO
- Identify yourself with a fictitious email address:
The server response to the command ‘rcpt to’ will give you an idea whether the email address is a valid one or not. You will get any one of the following response:
- OK – The recipient’s email address is a valid one
- 550 Error – Either recipient’s email address is disabled or it doesn’t exist.