Check if domain exists

[sinnbeck]

Unsure if this is already built in and I simply am unaware. Let's say a user sends to a non-existent domain. I would assume this would give an instant permanent fail. Instead it just gives a soft-fail and tries to send again several times. And when it finally fails, it will just report that it tried to many times. A "550 Domain not found" error would in this instance be better

I tested sending to [email protected] which i am certain does not exist :)

If I send to this address using gmail or similar mail providers, it will give an instant permanent fail due to the domain not existing.

[sinnbeck]

The same problem occurs on domains that exists but does not have an MX record.

[willpower232]

You can see how this is handled here

postal/lib/postal/smtp_sender.rb

Line 158 in 2e7aaab

rescue Net::SMTPServerBusy, Net::SMTPAuthenticationError, Net::SMTPSyntaxError, Net::SMTPUnknownError, Net::ReadTimeout => e

I imagine it would be difficult to tell the difference between "this domain does not exist" and "this domain is having a temporary DNS failure" without adding extra code so if you are unable to trust your users to enter correct domain details then you should probably include some extra validation in your system.

[sinnbeck]

I see what you mean. I just figured it would fail instantly. I suppose I am just too used to services like mailgun, where it fails right away :)