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550 5.1.0 "sender rejected" error message when I send email to a comcast address

New Poster

550 5.1.0 "sender rejected" error message when I send email to a comcast address

Greetings,

 

I’ve set up an email server on Amazon EC2 and it’s working well -- except for sending emails to <someone>@comcast.net.

 

Whenever I send an email, the following is in my response:

 

This is the mail system at host localhost.

 

I'm sorry to have to inform you that your message could not

be delivered to one or more recipients. It's attached below.

 

For further assistance, please send mail to postmaster.

 

If you do so, please include this problem report. You can

delete your own text from the attached returned message.

 

                   The mail system

 

<username@comcast.net>: host mx1.comcast.net[68.87.26.147] said: 550 5.1.0

    <myself@mydomain.net> sender rejected (in reply to MAIL FROM command)

 

Reporting-MTA: dns; localhost

X-Postfix-Queue-ID: F3B5861A65

X-Postfix-Sender: rfc822; myself@mydomain.net

Arrival-Date: Tue, 24 Dec 2013 22:04:42 -0800 (PST)

 

Final-Recipient: rfc822; username@comcast.net

Action: failed

Status: 5.1.0

Remote-MTA: dns; mx1.comcast.net

Diagnostic-Code: smtp; 550 5.1.0 <myself@mydomain.net> sender rejected

 

I spoke about this with a Comcast representative today, who told me that the problem is on my side, but I continue to find that hard to believe, because email recipients at all other ISPs, including at least gmail, yahoo, sbcglobal, and many others, receive emails just fine from my domain.

 

Additional info: I’m sending the email to my own Comcast email address (I have business internet through Comcast). I have the option to retain spam turned on, and the emails don’t end up there or anywhere else in my account. In fact, emails to the tech with whom I spoke today bounce in the same manner, and she didn’t receive them. Email client is Thunderbird for Windows 7, v24.2.0. My domain has been set up with reverse DNS (and again, emails to all other ISPs have gone through).

 

There is one thread on this forum that seems to describe the same problem as mine (http://forums.comcast.com/t5/E-Mail-and-Xfinity-Connect-Help/550-5-1-0-error-message-when-I-send-a-e... but there’s only one response, by a Comcast representative, asking for private contact.

 

Any advice or assistance would be most appreciated.

 

Bronze Problem Solver

Re: 550 5.1.0 "sender rejected" error message when I send email to a comcas


daywit wrote:

Diagnostic-Code: smtp; 550 5.1.0 <myself@mydomain.net> sender rejected

 

I spoke about this with a Comcast representative today, who told me that the problem is on my side, but I continue to find that hard to believe, because email recipients at all other ISPs, including at least gmail, yahoo, sbcglobal, and many others, receive emails just fine from my domain.


Comcast checks the validity of the sender email domain and refuses email from invalid sender domains. Lots of outfits don't bother with that check, which would explain why those other outfits would accept email with an invalid sender domain. We could check the DNS situation if you'd share the actual domain name.

New Poster

Re: 550 5.1.0 "sender rejected" error message when I send email to a comcas

Thanks, Steve. Something popped out at me after my original post:

    Reporting-MTA: dns; localhost

 

Given this, I changed my postfix server slightly so that this is my domain instead of localhost, and bing! Emails to comcast now work.

 

FWIW, my domain is dnziemba.net.

 

Thanks for the quick response!

 

New Poster

Re: 550 5.1.0 "sender rejected" error message when I send email to a comcas

More specifically (now that I have the time to write about it), the postfix $myhostname in /etc/postfix/main.cf was "localhost". Therefore, the Reporting-MTA line in the email showed "dns; localhost", and evidently the comcast mail server didn't like the fact that there is no actual public domain in that line, as indicated by the "550 5.1.0" error. I changed $myhostname to my domain name, and now comcast accepts emails from my server.