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ElRoc0_Tha_Gr81
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Friday, September 12th, 2025 1:54 AM

DMARC error messages

Whenever I send an email most of the time they get rejected and sent back with the following " remote server returned 550 5.7.509 access denied, sending domain comcast.net does not pass DMARC verification and has a DMARC policy of reject. Can anybody assist me with what to do about this issue. Or is it an issue with comcast.net? Things that I've had this email address for approximately 30 years maybe? I do not want to have to change it and change all my contacts and update them. 

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strega7

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4 months ago

How are you sending the emails?  

I assume you can send emails through the xfinity webmail page. Using their webmail or their SMTP server should work.  However, if you are using someone else's server, it should not work.

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ElRoc0_Tha_Gr81

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 actually use I gmail where I have it forwarded to. Have for years. Just started having issues very recently.

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4 months ago

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strega7

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DMARC tells the receiving server that the email is spoofed.  However, it does not distinguish spoofing for good versus spoofing for evil and doesn't make any allowances for the fact that someone may have spoofed their own address for years.

I spoofed email addresses in the 80s and 90s too.  Somewhere around 2010, I noticed that some emails were not getting through.  I believe some email systems were already doing ad-hoc spoofing detection at that time. DMARC has formalized this and is now becoming the norm.  In my case, I was spoofing my own address at my own domain, but I realized this was basically historical, going back to a time when SMTP had no authentication and ISPs were blocking port 25.  But these things had since changed so all I had to do was point my email client at the SMTP server for my domain, and my emails now pass DMARC.

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4 months ago

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BruceW

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4 months ago

What @strega7 said. A more technical description of Comcast/Xfinity's DMARC policy is given by @XfinityAlex at https://forums.xfinity.com/conversations/email/notice-dmarc-policy-for-comcastnet/667075ff729ad353204c8409.

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XfinityBenny

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4 months ago

@ElRoc0_Tha_Gr81 Thanks for adding a post. That is strange indeed. Are you using your email on the Xfinity website, or through an email app? 

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ElRoc0_Tha_Gr81

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actually use I gmail where I have it forwarded to. Have for years. Just started having issues very recently. It's always worked until very recently.

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4 months ago

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XfinityAlex

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@ElRoc0_Tha_Gr81​ This would have started several months ago, presuming the destination honors DMARC.  Not all do, and therefore it may have continued to work until now.

I believe Gmail has an option to send messages through our platform when acting as "comcast.net".  If you can't find this option, let me know and I'll dig a bit more.

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4 months ago

XfinityJeff

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Good morning @ElRoc0_Tha_Gr81, I hope you are having a good weekend so far. There is some good information in the link that was posted by @BruceW. Have you tried using the Xfinity website to email and see if the issue is happening their also?

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4 months ago

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ElRoc0_Tha_Gr81

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Not yet. I will and report back.

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4 months ago

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XfinityQuemekia

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@ElRoc0_Tha_Gr81 Let us know how it goes.

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4 months ago

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kbug62

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22 hours ago

I am an Xfinity user. I can email people using the webmail. I get this error message back from 2 people's email when I use my calendar function to set up a meeting but not the other's emails. Is it me or them? It says COMCAST does not pass the DMARC test. How do I fix this?

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XfinityAlex

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@kbug62​ Without the actual text of the error message, it's a bit hard to say.  I suspect they're forwarding the emails, and it's breaking message authentication somewhere along the way.  If you'd prefer, you can send me a DM with the contents of the error message.

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21 hours ago

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kbug62

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Dont know how to DM you. First timer.

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21 hours ago

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kbug62

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21 hours ago

Error Icon

Message blocked
Your message to [Edited: "Personal Information"] has been blocked. See technical details below for more information.

The response from the remote server was:

550 5.7.509 Access denied, sending domain [COMCAST.NET] does not pass DMARC verification and has a DMARC policy of reject. [LV5PR05MB998346.namprd05.prod.outlook.com 2026-01-08T12:27:09.932Z 08DE4D83D78766FB] [BYAPR08CA0072.namprd08.prod.outlook.com 2026-01-08T12:27:08.973Z 08DE4E8879CCB16D] [SJ1PEPF0000231D.namprd03.prod.outlook.com 2026-01-08T12:27:09.956Z 08DE4E848D0A0770]

(edited)

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