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I recently changed registrars and DNS location from Tucows to Cloudflare for one of my domains. During the change, Cloudflare copied my existing DNS records including SPF, DMARC and DKIM keys. The actual email server did not change.

Prior to the DNS/registrar change, emails from the domain worked fine. Now, after the change, any emails to Yahoo are returned as spam. I have other domains on the same email server that were not migrated that continue to work fine, so I'm pretty sure it has nothing to do with the mail server, only the DNS entries.

I've used MXtoolbox to verify the SPF, DMARC and DKIM keys and they all come back fine (ie. "pass").

At this point, I'm not sure what to do next to troubleshoot this. Is there something in the returned message I should be specifically looking for?

Here's the typical Yahoo response in the returned email:

host mta5.am0.yahoodns.net [98.136.96.75]
Delay reason: SMTP error from remote mail server after pipelined MAIL FROM:<email_address@example.com> 
SIZE=5650:    421 4.7.0 [TSS04] Messages from 209.182.201.150 temporarily deferred due to unexpected volume or user complaints - 4.16.55.1; 
see https://postmaster.yahooinc.com/error-codes

Additional edit

The DMARC XML report returned by Yahoo shows "Pass" for the DMARC, SPF and DKIM records.

MXToolbox excerpt:

X-Get-Message-Sender-Via: ngx249.inmotionhosting.com: authenticated_id: email_address@example.com
X-Authenticated-Sender: ngx249.inmotionhosting.com: email_address@example.com
X-Originating-IP: 192.145.239.210
X-SpamExperts-Domain: ngx249.inmotionhosting.com
X-SpamExperts-Username: 192.145.239.210
Authentication-Results: servconfig.com; auth=pass smtp.auth=192.145.239.210@ngx249.inmotionhosting.com
X-SpamExperts-Outgoing-Class: unsure
X-SpamExperts-Outgoing-Evidence: Combined (0.41)
X-Recommended-Action: accept

DKIM Selector:

v=DKIM1; k=rsa; p=blahblahblah

DKIM Signature from email header:

v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=example.com; s=default; h=Content-Type:MIME-Version:Message-ID:Date:"
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    When you say "Cloudflare copied", was that an automatic thing or did someone get the zone file and help you migrate it? (It would seem a bit of a long shot, but maybe their is a problem with the DKIM selector. I posit that while it is possible to guess the selector this is nowhere close to fullproof, and it may not be possible to deduce without access to the zone file)
    – davidgo
    Nov 26, 2022 at 7:39
  • This may not be something that MX toolbox could verify either, as the selector is indicated by the mail server when it sends outbound messages - unless you sent an email to MXtoolbox it probably can't tell you if the correct selector exists in DNS - ie the web interface doesn't have enough information.
    – davidgo
    Nov 26, 2022 at 7:41
  • Out of my area of expertise (I don't like or "do" Google) but I vaguely recall GMAIL has information about the authenticity of the email. If you can send an email to GMAIL and have a look at it, it might give you some clues - especially if it lands in the spam folder.
    – davidgo
    Nov 26, 2022 at 7:44
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    UPDATE: This problem currently appears to be resolved. Emails appear to be working again. It may have just been Yahoo or even blacklisting as Kate has suggested. It's not the first time we've seen problems with Yahoo's email service reject emails. I'll follow up again in a couple of days with an update in case things change again.
    – Trebor
    Nov 28, 2022 at 1:23
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    @Trebor It would be worth putting something like that in an "answer". (Comments are easily missed.) To clarify, nothing further has changed with the DNS? So it's possible that it was just coincidental that it coincided with a DNS change?
    – MrWhite
    Nov 28, 2022 at 1:38

2 Answers 2

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The problem could be IP reputation. The message is rather clear. The specific IP address (209.182.201.150, I assume it's your mail server) is being rejected.

Plus, that IP address is present in at least one blacklist, see in Mxtoolbox for example: https://mxtoolbox.com/SuperTool.aspx?action=blacklist%3a209.182.201.150&run=toolpage

Probably, that's the reason. Many mailservers are using blacklists and will refuse E-mail from IP addresses that are blacklisted.

This could be through no fault of your own, especially in shared hosting environments. Sometimes large blocks are blacklisted for wrong reasons and you could be a collateral victim. It's also possible that this address was previously assigned to another customer and accumulated bad history in the past.

I recommend that you try to get delisted. The website for the Uceprotect blacklist should be http://www.uceprotect.net/ but currently not resolving for me.

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    This may all be true, but it doesn't explain why there wasn't a problem until the DNS migration. The server is a shared hosting environment and has always had some level of black listing. That's why I set up the DMARC, SPF and DKIM keys.
    – Trebor
    Nov 26, 2022 at 16:23
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    You say you have other domains on the same email server, but do you actually send mail to Yahoo from any of those other domains? If the outgoing IP address is the same, then I would expect that Yahoo would behave the same.
    – Kate
    Nov 26, 2022 at 17:43
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    @Kate I think the point is tbat while tje DND has changed, the mail server has remained the same - so the issues are DNS, not IP related (returned error code notwithstanding)
    – davidgo
    Nov 26, 2022 at 18:44
  • Yes, I have tested sending emails to Yahoo from other domains that are on the same email server.
    – Trebor
    Nov 26, 2022 at 19:12
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    @MrWhite, that is correct. The latest tests from the other domains are correctly being delivered.
    – Trebor
    Nov 28, 2022 at 1:17
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UPDATE:

This problem currently appears to be resolved. Emails appear to be working again. It may have just been Yahoo or even blacklisting as Kate has suggested. It's not the first time we've seen problems with Yahoo's email service rejecting emails. I'll follow up again in a couple of days with an update in case things change again.

Just to clarify, no further DNS changes were made.

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