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Saturday, November 5th, 2022 7:09 PM

Cannot email comcast.net from my private domain exchange email server

Cannot email comcast.net from my private domain exchange email server.  This started recently.  
Keep getting this reply: 

Remote Server at comcast.net (2001:558:fd01:2bad::4) returned '400 4.4.7 Message delayed'
11/4/2022 3:27:27 AM - Remote Server at comcast.net (2001:558:fd01:2bad::4) returned '451 4.4.0 Primary target IP address responded with: "554 resimta-a1p-087338.sys.comcast.net resimta-a1p-087338.sys.comcast.net xxx.xxx.xxx.xxx found on one or more DNSBLs, see http://postmaster.comcast.net/smtp-error-codes.php#BL000010." Attempted failover to alternate host, but that did not succeed. Either there are no alternate hosts, or delivery failed to all alternate hosts. The last endpoint attempted was 2001:558:fd01:2bad::4:25'   

I have gone through the process of removing block on ip address at comcast.net and their reply is it is not being blocked.  I am also not on any spam lists, have what seem to be correct spf, dmarc, dkim records for my domain.   Thanks in advance.

I am a customer of comcast business class internet and have spent time with Tier II support on this issue.  

A ptr record was added but that did not fix the issue.  They said it needs to be fixed at the Xfinity end.  I can't post question on their support board because I do not have Xfinity internet.

Official Employee

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92 Messages

2 years ago

@user_cae7a3 Thank you for taking the time to reach out to us here on our Xfinity Forums. I can definitely take a look at the account. It sounds like we may need to get a ticket open though. Please send us a DM with your full name and address to Xfinity Support. 

 

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