![]() Some clients use a hostname reported by the OS (which may or may not bear any resemblence to a hostname that has any meaning on any network), some use their local IP address. ![]() The client has to use something as the hostname since the protocol requires it to send one but a desktop system may not have a meaningful hostname. Typically on modern mailservers it records in the "hostname" field of the header both the "hostname" reported by the client along with the actual IP address and/or reverse DNS hostname seen by the server.Ĭoming forward to the modern world we now use desktop email clients. The receiving mail server adds a "Received:" header to document the path the mail took. These big multi-user computers would have had a well-defined hostname. Networked email started it's life as a way of interconnecting the local email systems in use on big multi-user computers. "personal computers" as we know them today didn't exist back when SMTP was created. The world back then was also much more trusting, noone expected people to deliberately lie about their identity. Why have the client send the hostname to the server? because SMTP was designed to run over many transport protocols, some of which may not provide ways for the server to identify the client. This command has a field for the senders hostname. When a SMTP client sends a mail to a SMTP server it starts out with a "helo" or "ehlo" command. Pick a risk-free HMA plan with our 30-day money-back guarantee. 75 GET HMA VPN 30-day money-back guarantee Starting from 2.99/mo Try for 7 days How to set up HMA VPN for Windows Need help Check out our support page. This is slightly different to what other answers have discussed, which are related to actual SMTP servers using private addresses to transport email inside an organisation. Download HMA VPN for Windows The secure VPN client for Windows 7, 8, 8.1, 10, and 11. ![]() Using the IP address probably provides a bit more privacy as some people may argue seeing 172.1.2.3 in the headers is better than MIKES-MACBOOK or CEO-WORKSTATION.Īt the end of the day the client just needs to provide something reasonable in the HELO command, and some clients choose the IP address. ![]() For example you often see headers like the following: Received: from DESKTOP9U6J0BC (unknown) For sending email, servers will normally accept anything as long as you are authenticated (you can't expect end users to all have real, valid hostnames configured on their machines).įor SMTP clients like Outlook, they could send your machine name, but that isn't fully qualified and might not be desirable depending on what the machine is called. The easy-to-use app for Windows 10 or below comes with a range of features including auto-connect, dedicated servers for streaming content, and P2P download support. For inbound email, many servers actually verify the HELO hostname to make sure it's valid and the DNS matches. HMA is a paid VPN service that helps protect your privacy and online activity. Received: from (.address)"Īs you mentioned in the comments, the private IP in this particular location is because it was sent as the clients hostname in the HELO command.įor proper mail servers, the HELO command should include their fully qualified hostname, which should also match with DNS. ![]()
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