Contributor
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19 Messages
Comcast Email Server Misconfiguration
Comcast/Xfinity email cannot deliver messages to recipients at diocal.org. Messages bounce back with a DNS configuration / lookup error from Comcast’s outbound mail servers.
This occurs consistently when sending from my Comcast address. Sending to the same recipients from Yahoo Mail succeeds, so the destination domain is reachable and accepting mail.
This appears to be a Comcast outbound SMTP / DNS / MX resolution issue, not a client or device problem. Rebooting or changing mail clients does not apply.
Here is the error message (name edited for privacy):
Your message did not reach some or all of the intended recipients.
Subject: test message
Sent: 1/22/2026 1:40 PM
The following recipient(s) cannot be reached:
'xxxxxxxxx@diocal.org' on 1/22/2026 1:40 PM
Server error: '550 5.1.1 <xxxxxxxxx@diocal.org> Domain unrouteable, possible DNS misconfiguration'
Requesting escalation to Email Operations / Mail Engineering to investigate Comcast’s outbound mail handling for the diocal.org domain.
user_17b940
Visitor
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2 Messages
2 days ago
I am having a similar issue. I have had two emails bounce back today to people I have emailed multiple times and never had an issue with the email going through. They were two different destination domains.
The bounce back response I am receiving is:
Reason: Unroutable destination domain:
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NotHerbert
11 Messages
2 days ago
I am having the exact same problem this afternoon (as of about 2 pm est) sending to recipient addresses that I email every day.
5.1.1 <name@domain.com> Domain unrouteable, possible DNS misconfiguration
Attempting to send to three addresses (and counting) causes outgoing mail to simply NOT SEND. (These 3 are in a group of 5; I am able to reach the other 2 without issue, so it is certain domains that are tripping this up.)
As DRM said above, the email goes through without issue using another sending address outside of the Comcast family.
I did just log into my account on the xfinity site and saw a "your email is almost full!" message. I will deal with that separately but it does not seem to be related to this issue (especially since I can email to SOME but not to OTHERS).
Please repair!
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Lbg13
Visitor
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13 Messages
2 days ago
Same problem today. Seems when replying if you manually copy and paste the email address without <…..> around it like the reply adds it works??
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user_nm2nsv
Visitor
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2 Messages
2 days ago
same thing happening in Maine to email addresses at bowdoin.edu I just tried sending some test messages directly from the comcast server and at least so far am not getting the bounce back messages. Normally I'm sending from Outlook and having the DNS problem. Are others here using Outlook or another third party email program or are you still having the problem emailing directly from the server? I'm on the phone with comcast now.
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XfinityThomasA
Official Employee
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3.2K Messages
5 hours ago
Hello, and thank you for joining the Xfinity Forums community for help with your email, DRM_SF. All active comcast.net email accounts, including those used by current and former Xfinity customers, will have the option to upgrade to Yahoo Mail. Are you experiencing this after upgradeding your Comcast.net email experience to Yahoo Mail?
Upgrade your Comcast.net email experience to Yahoo Mail
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