If you send an email with your VPN connected I believe the recipient should see the VPN IP address in the email header, not the real IP address. But if the recipient replies to this email at a later point in time when your VPN is not connected, is your real IP address exposed in some way to their view? Or does the reply email continue to refer only to the VPN IP address shown in the original sent email, even though your VPN is no longer connected at that point?
Question 1: What IP Address recepient will see?
Scenario 1: You are connected to VPN and using a native email client such as Outlook: Then the header will contain the VPN IP Address
Scenario 2: You are connected to VPN and using a webmail service such as Gmail: Your real IP address or VPN IP address will not be part of the headers. Headers will only contain your webmail servers IP address.
Question 2: Will the real IP address be exposed when recipient replies?
Recipient will reply to your email address not your IP address. Let me elaborate. Emails are stateless, every reply or forward will be just considered like a normal email by your mail server. When the recipient will respond to you, recipient's email server will fetch the MX record from your DNS records. The recipient's email server will then send this email to your email server. Now, for you to access this email, you will have to sync your native email client with your server or access this email through webmail. This is what I meant by "Recipient will reply to your email address not your IP address".
Here is my understanding of what is happening in the internet world. Consider email servers are similar to post offices. Now you hire an undercover agent whose job is to collect/send information on your behalf without disclosing your real identity.
Now coming back to your question. Email servers track the information of where the email is coming from using the header called "Received: From". The recipient of the email will have the IP address of your private VPN. Now when he replies the message is collected by the email server and it will be sent to you when you request for it.
Now if you again send a reply to your recipient with your VPN on only that IP will be tracked.
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