Question

Am developing and newsletter email software in vb.net for a friend, and he has asked me to add option to send email using dns servers,

How do i send an emai using dns server without smtp or imap?

Answer 1

Send email “using DNS servers” still uses SMTP. And it’s generally a bad idea. Here’s what it’s about:

Usually, an email app (your own, Outlook, etc.) send mail using SMTP or similar protocol to a configured mail server. It could be a company’s own server, or an ISP’s server, or something like that. The mail may pass through various outgoing mail servers on its way out of an organisation, but at some point it hits a “boundary server” (There are pretty names for all these different types of server, but they’re not important right now.)

This boundary server uses DNS to find the recipient’s mail server and then sends the message (using SMTP) to that server. (I have omitted the details on purpose)

Sending email “using DNS” means that your app acts as a boundary server. It uses DNS to find the recipient’s mail server and then sends the mail directly – rather than using any outgoing servers.

It’s a bad idea for two reasons.

1. More and more ISPs block SMTP traffic that doesn’t pass through their outgoing servers
2. More and more incoming servers validate the boundary server using various techniques. Your app is not likely to be accepted by these servers

Both of these issues are anti-spam countermeasures, so using this technique makes you look like a spammer, leaves many of your messages blocked, and is likely to get your IP address blacklisted.

Hopefully you can explain this to your friend so that they will understand that the “normal” way of sending mail is the only way to ensure that they don’t get listed as a spammer.