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550 5.1.0 Invalid sender domain when sending to comcast domain using mailgun

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New Poster

550 5.1.0 Invalid sender domain when sending to comcast domain using mailgun

I use mailgun to send emails from my website and all emails to any comcast addresses are failing with an error.  I have seen other people have the same issue on this forum and have read the posts, but am not sure what to do.  One of them suggested adding a MX record to my DNS which I did, but still failing.  I only just added the MX record, so maybe I need to give it time to propagate through the systems??...  Anyway, hoping someone else has fixed this issue and can help.

 

Failed: user***@mydomain***.com → recipient***@comcast.net 'Your order was refunded' Server response: 550 550 5.1.0 Invalid sender domain

 

 

Here is the mailgun log:

 

{
  "severity": "permanent",
  "tags": [],
  "storage": {
    "url": "https://api.mailgun.net/v2/domains/****/messages/****",
    "key": "*****"
  },
  "delivery-status": {
    "tls": true,
    "mx-host": "mx1.comcast.net",
    "code": 550,
    "description": null,
    "session-seconds": 8.528867959976196,
    "message": "550 5.1.0 Invalid sender domain",
    "certificate-verified": true
  },
  "recipient-domain": "comcast.net",
  "event": "failed",
  "campaigns": [],
  "reason": "generic",
  "user-variables": {},
  "flags": {
    "is-routed": null,
    "is-authenticated": true,
    "is-system-test": false,
    "is-test-mode": false
  },
  "log-level": "error",
  "timestamp": 1466644057.906317,
  "envelope": {
    "transport": "smtp",
    "sender": "*****",
    "sending-ip": "198.61.254.13",
    "targets": "*****@comcast.net"
  },
  "message": {
    "headers": {
      "to": "******",
      "message-id": "*****",
      "from": "*******",
      "subject": "Your order was refunded"
    },
    "attachments": [],
    "recipients": [
      "*****@comcast.net"
    ],
    "size": 1260
  },
  "recipient": "*****@comcast.net",
  "id": "******"
}

 

Accepted Solution

Re: 550 5.1.0 Invalid sender domain when sending to comcast domain using mailgun

I think I have finally solved my problem.  I actually dug through my email logs and found that cox.net was also failing.  However, they gave a different error message.  

 

550 5.1.0 <bounce+472485.63258-XXX=cox.net@mg.mydomain.com> sender rejected - Refer to Error Codes section at http://postmaster.cox.net/confluence/display/postmaster/Error+Codes for more information.

 

Anyway, with the help of that message and their error codes I was able to dig around some rackspace docs and figure it out.

 

It is an MX record that is needed...however, I had done it wrong.  Hopefully this will help someone in the future, so I am documenting it here.  I use Google Apps for normal emails, but also Mailgun.  I had all the Google Apps MX records, but what I had to do was add an additional MX record with a subdomain of "mg" for mailgun, which I just pointed at google server.  Here are my MX records, which seem to now be working:

 

MX Records
Mail Server Preference Subdomain TTL  
aspmx.l.google.com 1   Default  
alt1.aspmx.l.google.com 5   Default  
alt2.aspmx.l.google.com 5   Default  
alt3.aspmx.l.google.com 10   Default  
alt4.aspmx.l.google.com 10   Default  
aspmx.l.google.com 20 mg Default  
View answer in context
Email Expert

Re: 550 5.1.0 Invalid sender domain when sending to comcast domain using mailgun

I would call Comcast security for this -------------------------

 

Comcast Customer Security Assurance-------------------

Normal business hours (6:00 am to 2:00 am EST, 7 days a week)

1 - 888-565-4329

 

 

 




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New Poster

Re: 550 5.1.0 Invalid sender domain when sending to comcast domain using mailgun

Thanks for your reply!  I called comcast number provided and unfortunately they were not all that helpful.  They insisted that the issue was not on their side and that I needed to contact my email provider.  I will do that and keep everyone posted.  I am a little confused as to why it would work for every email server, but comcast if it wasn't something I needed to do on their side.  Anyway, we'll see what rackspace says.

Gold Problem Solver

Re: 550 5.1.0 Invalid sender domain when sending to comcast domain using mailgun


boomer196 wrote: ... I called comcast number provided and unfortunately they were not all that helpful. ...

Unfortunately, that's common with the first-line reps at CSA. If your mail host doesn't help you and no employee stops by here to help out, there isn't much you can do except call them back, be persistent, and keep at them until you get a satisfactory answer.

New Poster

Re: 550 5.1.0 Invalid sender domain when sending to comcast domain using mailgun

I think I have finally solved my problem.  I actually dug through my email logs and found that cox.net was also failing.  However, they gave a different error message.  

 

550 5.1.0 <bounce+472485.63258-XXX=cox.net@mg.mydomain.com> sender rejected - Refer to Error Codes section at http://postmaster.cox.net/confluence/display/postmaster/Error+Codes for more information.

 

Anyway, with the help of that message and their error codes I was able to dig around some rackspace docs and figure it out.

 

It is an MX record that is needed...however, I had done it wrong.  Hopefully this will help someone in the future, so I am documenting it here.  I use Google Apps for normal emails, but also Mailgun.  I had all the Google Apps MX records, but what I had to do was add an additional MX record with a subdomain of "mg" for mailgun, which I just pointed at google server.  Here are my MX records, which seem to now be working:

 

MX Records
Mail Server Preference Subdomain TTL  
aspmx.l.google.com 1   Default  
alt1.aspmx.l.google.com 5   Default  
alt2.aspmx.l.google.com 5   Default  
alt3.aspmx.l.google.com 10   Default  
alt4.aspmx.l.google.com 10   Default  
aspmx.l.google.com 20 mg Default  
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