Email error 554 5.1.2

Since switching my DNS to Cloudflare, I’ve had one client in particular say that many of their industry contacts are having their emails rejected. My client is able to send, but when their contacts reply or send an email on their own its immediately bounced back with Error 554 5.1.2

My understanding is that this message says the mailbox account of the particular user cannot be found. I’m sure I’ve got something set wrong in my Cloudflare setup, as when I point the nameservers to the hosting account, or registrar, it all seems to work.

Are there any first steps or common pointers I could follow to help self-diagnose this issue? I’ve looked online, and found many instances of 554, but very few of 5.1.2.

Any help is greatly appreciated.

Hi there,

In terms of email by default, he only part Cloudflare plays is responding to DNS queries. We do not proxy or intercept email traffic in any way - so should not affect the delivery of email as long as your DNS records are configured correctly. If your receiving email from other sources, just not from one client - then this makes me think the DNS records are fine.

If you are getting an error that says ‘User cannot be found’ this normally would point to something wrong with the mail server and require your mail admin to check the status of that users mailbox and also to check any mail logs to see if they can see these mails being recieved to the mail server.

Cloudflare has this support guide on how your DNS should be configured, however based on what you said this does not sound like a DNS issue.

Email undeliverable when using Cloudflare

If you are still having an issue, providing any raw mail headers from the failed message may help identify where the problem may be.

Hi,

I am getting a user not found error, however this seems to only be happening when the sender is using ProofPoint (*.pphosted.com). The domain in question had its name servers pointed to my WHM/cPanel host - when I added the domain to Cloudflare, CF replicated the DNS records from cPanel - with one exception.

Rather than the MX record being mail.domain.com or just domain.com, CF created a dc-#########.domain.com entry. From the page you linked it explains why this happens, and as it doesn’t appear to be an issue for any users other than those using ProofPoint, I had thought it to be ok.

On the mail server itself, accounts exist, aren’t full, and are receiving email from multiple other sources. I don’t want to get into a finger pointing match, as everyone loses then. Just hoping to find some clarity as to why this is happening and how to fix.

Thanks for your time, any further ideas?

Create an Mx record (host) which is not proxied / orange clouded.

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The MX record is set to DNS only. I’ve tried both CNAME and A record for mail.domain.com (not at the same time obviously). Both of those were also grey clouded.

If I left either with the Orange cloud, I couldn’t send/receive email at all.

I am getting a user not found error, however this seems to only be happening when the sender is using ProofPoint (*.pphosted.com).

This points to an issue with your mail server somehow and not an issue with your DNS records. I would get your mail server administrators involved to look at the mail logs and try to understand what is going on here.

I thought that too, however there are no logs on the mail server to indicate that the message ever got that far on our end. The senders IT department would only provide us with the bounce back message, nothing from their logs. As I couldn’t find a solution within an acceptable period of time, I’ve moved the nameservers away from Cloudflare and all email resumed without issue.

Really just trying to understand what was happening here as I’d like to use Cloudflare moving forward for my clients. Is there a way to test whether the sender was somehow being blocked by other Cloudflare services? MX wasn’t being proxied, so I wouldn’t think that would have been an issue. Mostly grasping at straws here.

Looking up the MX record with MXtoolbox kept reporting the hostname was _dc-mx.############.domain.com Not sure if this would cause issue or not.

The advice from earlier is correct: Create an “A” record for the ‘mail’ subdomain and set it to :grey: DNS Only. At that point, secure connections should have a consistent hostname and SSL certificate. And be a direct connection, and all that other good stuff. It’s the right way to set up mail DNS records.

MX records can never be set to :orange: Proxied. It’s like a TXT record.

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Hi @design3 I guess you’re right, we are experiencing the same issue, and confirm that the problem occurs only when the sender is using ProofPoint.
Remote server returned '554 5.1.2 <_dc-mx.xxxxxxxxxxxxxxx.example.com

@Damian please help we are still facing this problem…

If your seeing a * <_dc-mx.xxxxxxxxxxxxxxx.example.com* record then mail records are not configured correctly. I suggest watching the video on this KB - Email undeliverable when using Cloudflare – Cloudflare Help Center

The DNS Record that your MX record points to needs to be grey-clouded.

I’m not sure if this will fix the issue, but it is the only thing that may possibly Cloudflare to interfere with the delivery of your mail.

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