We had been getting these messages when customers try sending us emails.

This is an automatically generated Delivery Status Notification



Delivery to the following recipient has been delayed:


Message will be retried for 2 more day(s)

Technical details of temporary failure: Google tried to deliver your message, but it was rejected by the server for the recipient domain ital.com by mail.ital.com. [].

The error that the other server returned was: 450 4.1.8 <myEmail@example.pro>: Sender address rejected: Domain not found

Googling this issue leads to cases which say that the problem isn't my servers problem, but it's the customers server that has trouble finding my server:

Email Bounces: Sender address rejected: Domain not found



The thing is That this isn't the only customer that gets this error message.

The changes we made lately with our DNS:

I have 2 hosted zones on amazon aws:

.COM domain:

Last Change - We had an MX record pointing on google emails, and we added some new outlook records (SRV, CNAME and TXT) so we can get email to outlook too. We removed the DNSs after 2 monthes because no one likes using outlook in the office.

One before last change - We added an A record to create this sub-domain tools.example.com on Route 53, added a <VirtualHost *:80> on my Ubuntu server. Following this: Create a sub-domain using Amazon AWS vs Creating the sub-domain from within the server - What's the difference?

.PRO domain:

One before BEFORE last change - Using S3 on Amazon AWS and Route 53, we 301 redirected the .PRO domain to the .COM domain.

In general: The .PRO has an MX record that points on the MX record in the .COM . Which always worked properly.

Following this post I created: https://stackoverflow.com/questions/32971789/how-to-redirect-an-old-domain-to-a-new-one-while-not-having-any-server-for-the

Just an A record won't cause a redirect. For that, you need a web server in the mix. AWS has a service that can do this for you without having to maintain and pay for such a server.

Create an empty bucket in Amazon S3, named www.example.pro and another named example.pro. The bucket names must exactly match the domain, with and without www.

In each bucket, under static website hosting (in bucket properties), and choose "redirect all requests to another domain."

In the "redirect all requests to" box, put example.com. (Or www.example.com, the same name in both, wherever you want the users to be redirected to.

Create a hosted zone in Route 53 for example.pro.

Create two A records, one with the hostname empty, select "Yes" for "Alias" then choose the S3 endpoint from the selection box below.

Switch your DNS nameservers with the registrar for the .pro domain to the 4 nameservers that Route 53 assigned to the new hosted zone.

You're done.

S3 is, of course, primarily for storage... but this web site redirection capability is a secondary feature designed for exactly this purpose.

Can someone help me debug this problem, This is extremely urgent!

  • Can check with your domain name here: MxToolbox, if it's properly configured and reachable? – Diamond Nov 11 '15 at 9:29
  • Whos is getting the bounced messages? You or the customer? – Diamond Nov 11 '15 at 9:36
  • @bangal I tested on MXToolbox and I get a positive output. The customer is getting the bounce errors. Most of the emails we get are fine, but there is more than 1 customer that is experiencing this and might be something with our DNSs – Rick Sanchez Nov 11 '15 at 9:43
  • If it is working for most of the domain then I would guess your configuratioin is ok. May be you can try whitelisting the problem customers domains in your mail server if it's possible. Moreover you can also check the customer domain in MxToolbox if they are properly configured. – Diamond Nov 11 '15 at 10:05
  • I'm using Google app mail so its a Google DNS in the MX – Rick Sanchez Nov 11 '15 at 10:28

Web redirection has nothing to do with email routing, so this part you can ignore. It is 100% sure that 301 redirect has no impact on email communication. It is for HTTP protocol, http://en.wikipedia.org/wiki/HTTP_301.

The most important thing is proper DNS configuration. If you want mails addressed to yourdomain.pro domain to be accepted by yourdomain.com domain email server, you need to configure it accordingly. I think you should check your dns server for possible misconfiguration. There are many online utilities available out there to query the DNS servers and see if the received answer is correct/expected.

The error itself means, the mail server is unable to resolve the domain name of the particular sender.


In my opinion MX DNS config is OK since you already got an answer from SMTP server:

450 4.1.8 <myEmail@example.pro>: Sender address rejected: Domain not found

I would focus on SMTP configuration: Try allowing MTA to process messages from any domain.

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