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Forum Discussion
RBK50 DNS errors when sending to SMTP server
Latest firmware 2.7.4.24. When sending from Outlook or iOS clients, cannot send, error AUP-CXDNS. Shutting off wireless circumvents the issue. Any DNS setting in the ORBI that might correct this? Tha...
For a test, please try to select “Use These DNS Servers” and set the dns servers to primary 1.1.1.1 and secondary 8.8.8.8 then click on Apply
Will do, though since that would impact the household working from home, it will be (much) later today. Thanks.
Same failures when using the alternative DNS servers suggested. Now pursuing this as an issue with my ISP, which at the moment is a different ISP than my email provider.
Thanks for the help, and I'll share more later whether fixed or not.
Perhaps I read the conversation incorrectly. It appears that post #4
"email works normally when not connected to WiFi makes it hard (not impossible) to blame them"
is inconsistent with post #5
I will add that errors occur whether connected via ethernet or WiFi.
I found one comment that this condition was remedied by the ISP creating a PTR (whatever the heck THAT is)
(see post #2 on this conversation: https://www.reddit.com/r/CoxCommunications/comments/vs759s/smtp_outbound_server_from_outlook_when_not_on_cox/)
The sense that I get when looking up CXDNS under Cox on this website: https://mxtoolbox.com/Bouncebacks is that Cox is attempting to perform a Reverse DNS Lookup on the IP address that is attempting to connect to the SMTP server and not finding a PTR record.
When I input my public IP address into this DNS Reverse Lookup Site, this is what it shows:
cpe-xxx-xxx-112-236.socal.res.rr.com
What happens when you enter your public IP address into the tool?
https://mxtoolbox.com/ReverseLookup.aspx
CrimpOn wrote:Perhaps I read the conversation incorrectly. It appears that post #4
"email works normally when not connected to WiFi makes it hard (not impossible) to blame them"
is inconsistent with post #5
I will add that errors occur whether connected via ethernet or WiFi.
..............
What I understood is that email did not work when device was connected to home network but it worked when connected to other networks e.g. the mobile network.
SteveHansen26 wrote:Same failures when using the alternative DNS servers suggested. Now pursuing this as an issue with my ISP, which at the moment is a different ISP than my email provider.
Thanks for the help, and I'll share more later whether fixed or not.
Yes, I think the issue seems between your email provider and the home internet provider. Your email provider is doing an extra security check to validate that email is not coming from dial-up users or a dynamic IP space, which are methods used by spammers.
During a rDNS lookup, your SMTP server (provided by your email provider) verifies that your IP address matches the domain name submitted by the SMTP client in the HELO command. For some reason this is not being passed forward by the internet provider.
As a workaround, I think you can configure another SMTP server (hotmail, Gmail, .....) on your email client.
Ekhalil, you have it right, I believe, in both of your recent posts. Had the opportunity to test from Cox ISP with RBR50, and email is sent without issue. Seems clear that issue is with ISP from my original report and testing. Thanks again, all.
