Mail bounced due to DMARC error

[scletts1]

I can't send email from lineone to an address that is then redirected to gmail.

Here's the bounce message:

A message that you sent could not be delivered to one or more of its
recipients. This is a permanent error. The following address(es) failed:

xxxx@gmail.com
(ultimately generated from yyyyy@zzzzz.co.uk)
host gmail-smtp-in.l.google.com [173.194.219.26]
SMTP error from remote mail server after end of data:
550-5.7.26 Unauthenticated email from lineone.net is not accepted due to
550-5.7.26 domain's DMARC policy. Please contact the administrator of
550-5.7.26 lineone.net domain if this was a legitimate mail. To learn about the
550-5.7.26 DMARC initiative, go to
550 5.7.26 https://support.google.com/mail/?p=DmarcRejection 3f1490d57ef6-e39f6c458a4si7019159276.86 - gsmtp

Reporting-MTA: dns; raz.smoothhost.com

Action: failed
Final-Recipient: rfc822;yyyyy@zzzzz.co.uk
Status: 5.0.0
Remote-MTA: dns; gmail-smtp-in.l.google.com
Diagnostic-Code: smtp; 550-5.7.26 Unauthenticated email from lineone.net is not accepted due to
550-5.7.26 domain's DMARC policy. Please contact the administrator of
550-5.7.26 lineone.net domain if this was a legitimate mail. To learn about the
550-5.7.26 DMARC initiative, go to
550 5.7.26 https://support.google.com/mail/?p=DmarcRejection 3f1490d57ef6-e39f6c458a4si7019159276.86 - gsmtp

[Ady-TalkTalk]

Thanks for letting us know.

Ady

[Dangerous2a]

@Ady  Sorry for the delay.

The address of my contact is in the form fred@bloggs.family but the error that was returned was from that adddress with a note saying it came from <<fred.bloggs@btinternet.com  (ultimately generated from fred@bloggs.family)>>

Presumably there was some kind of forwarding going on by btinternet but that was transparent to the sender (me) and I have used the address many times before with no issues. 

I have since been able to use Gmail to contact him on the fred@bloggs.family  address but it was dumped into his spam folder by bt.

Fortunately he found it.

All very strange.

[Ady-TalkTalk]

It seems like there's still mail forwarding involved. You need to send the mail from TalkTalk webmail to just 1 email address directly and that should be working. 

Ady

[Dangerous2a]

Hi, @Ady-TalkTalk  Just tried  both ways and got bounced from Webmail and Outlook. The details are attached. Weird..

[Dangerous2a]

Hi @Ady-TalkTalk 

I did not try that as I never use Webmail. I will try 2 test sendings, one via Outlook and one via Webmail and report back.

Thanks.

[Ady-TalkTalk]

Hi Dangerous2a, if you send a mail from webmail direct to the email address do you still get the error?

Ady

[Dangerous2a]

Hi @ Ady I have had a similar rejection message to the above today:

<<Reporting-MTA: dns; cp160173.hpdns.net

Action: failed
Final-Recipient: rfc822;******@yyyyyyy.xxxxxx
Status: 5.0.0
Remote-MTA: dns; mx.bt.prod.cloud.openwave.ai
Diagnostic-Code: smtp; 571-DMARC Reject (5.7.1.2) on 2025/03/10 20:17:00 GMT from un-validated IP address: 91.238.160.173. The DMARC policy for the domain talktalk.net tells us to reject this email.
571 We protected our customers by not allowing any more emails from your IP address till we notice an improvement. You may have been affected unknowingly through your email provider. Please contact your email provider to assist. Our Postmaster will be unable to help you.>>

This seems to only be at this one receiving address, all other mail appears to go well enough. I simply replied to an incoming mail using the reply tab in outlook. The address is an unusual one but the error came from btinternet.com if that helps.

I have had and reported lots of spam/phishing emails over the last 6 months or so. Could this be the problem?

Any ideas?

[Ady-TalkTalk]

Send me a personal message with the affected email addresses please. 

Ady

[scletts1]

Hi Ady,

Thanks for your quick reply but I don't believe it deals with the issue.

You say "TalkTalk outgoing mail servers don't allow unauthenticated mail sending" but that isn't the problem, I can send mail OK, I use smtp.talktalk.net together with my lineone address and password.

The problem only happens when I send to one particular address. The user redirects his emails to gmail, which bounces messages from me. It does not bounce redirected email from other people.

The error message says the problem is at lineone. As I showed you in my first message it says, "Unauthenticated email from lineone.net is not accepted"

My mail is sent from an authenticated TalkTalk email domain, it is redirected by an intermediate server and is then bounced by gmail.

I don't understand what's happening, can you investigate some more?
Simon

[Ady-TalkTalk]

Hi scletts1, TalkTalk outgoing mail servers don't allow unauthenticated mail sending. The mail must be sent from an authenticated TalkTalk email domain. 

Ady