yahoo.co.k

JasonWard · 5 Feb 2007, 12:18 AM

I accidently sent an email to abuse@yahoo.co.k which Fastmail queued for delivery and then reported back to me many hours later as follows.

Code:

<abuse@yahoo.co.k>: host 10.202.2.150[10.202.2.150] said: 421 4.4.1 - No valid
    recipients (example error - 450 <abuse@yahoo.co.k>: Recipient address
    rejected: Domain not found) (in reply to end of DATA command)

Why?

Why didnt Fastmail just give me an error message by return saying the domain I used was invalid?

Jason

robmueller · 5 Feb 2007, 02:15 PM

Because transient DNS errors shouldn't cause your email to bounce, and in cases like this, it's not actually possible to know if the domain is temporarily unavailable or permanently unavailable.

DNS like email is supposed to be able to handle transient problems (eg in email if you get a 4xx response from the other side, you try and resend again later). So when you lookup a domain and don't get a response, the best thing is to keep the email queued and try again later.

Rob

5 Feb 2007, 12:18 AM	#1
JasonWard Cornerstone of the Community Join Date: Mar 2004 Location: London, UK Posts: 834	yahoo.co.k I accidently sent an email to abuse@yahoo.co.k which Fastmail queued for delivery and then reported back to me many hours later as follows. Code: <abuse@yahoo.co.k>: host 10.202.2.150[10.202.2.150] said: 421 4.4.1 - No valid recipients (example error - 450 <abuse@yahoo.co.k>: Recipient address rejected: Domain not found) (in reply to end of DATA command) Why? Why didnt Fastmail just give me an error message by return saying the domain I used was invalid? Jason

5 Feb 2007, 02:15 PM	#2
robmueller Intergalactic Postmaster Join Date: Oct 2001 Location: Melbourne, Australia Posts: 6,102 Representative of: Fastmail.FM	Because transient DNS errors shouldn't cause your email to bounce, and in cases like this, it's not actually possible to know if the domain is temporarily unavailable or permanently unavailable. DNS like email is supposed to be able to handle transient problems (eg in email if you get a 4xx response from the other side, you try and resend again later). So when you lookup a domain and don't get a response, the best thing is to keep the email queued and try again later. Rob