Emails are being returned as undeliverable

Question

Emails are being returned as undeliverable

M Douglas 0

I can't send any emails to adresses at gmail.com

and now to many other adresses

I get this message:- The following organization rejected your message: BL6PEPF0001AB4A.mail.protection.outlook.com.

0 comments

6 answers

Your answer

Answer 1

M Douglas 0

Does this help?

Diagnostic information for administrators:

Generating server: DU0PR10MB6653.EURPRD10.PROD.OUTLOOK.COM

******@outlook.com AM4PEPF00025F96.mail.protection.outlook.com Remote server returned '554 5.7.0 <AM4PEPF00025F96.mail.protection.outlook.com #5.7.515 smtp;550 5.7.515 Access denied, sending domain DBMAIL.COM doesn't meet the required authentication level. The sender's domain in the 5322.From address doesn't meet the authentication requirements defined for the sender. To learn how to fix this see: https://go.microsoft.com/fwlink/p/?linkid=2319303 Spf= Fail , Dkim= Fail , DMARC= None [DU5P191MB2406.EURP191.PROD.OUTLOOK.COM 2026-05-20T14:48:35.190Z 08DEB5D22BBE3A39] [PA7P264CA0308.FRAP264.PROD.OUTLOOK.COM 2026-05-20T14:48:35.199Z 08DEB61982916359] [AM4PEPF00025F96.EURPRD83.prod.outlook.com 2026-05-20T14:48:35.207Z 08DEB2A104B492DF]>'

M Douglas 0 Reputation points

2026-05-20T15:43:47.29+00:00

Sorry but my eyes cross just looking at this answer
M Douglas 0 Reputation points

2026-05-20T15:47:15.7866667+00:00

II just clicked on the link and found myself on the same page as this https://learn.microsoft.com/en-us/answers/questions/5897085/emails-are-being-returned-as-undeliverable?page=1&orderby=Helpful&comment=answer-12785609&translated=false
M Douglas 0 Reputation points

2026-05-20T15:48:37.8433333+00:00

I think it is called "going around in circles" the link takes me to my own question

Answer 2

this is a copy of the complete message

Undeliverable: Let me know if you get this

******@outlook.com

You

Delivery has failed to these recipients or groups:

[Michael Wright] Your message wasn't delivered. Please try resending the message.

The following organization rejected your message: AM4PEPF00025F96.mail.protection.outlook.com.

Diagnostic information for administrators:

Generating server: DU0PR10MB6653.EURPRD10.PROD.OUTLOOK.COM

******@outlook.com AM4PEPF00025F96.mail.protection.outlook.com Remote server returned '554 5.7.0 <AM4PEPF00025F96.mail.protection.outlook.com #5.7.515 smtp;550 5.7.515 Access denied, sending domain DBMAIL.COM doesn't meet the required authentication level. The sender's domain in the 5322.From address doesn't meet the authentication requirements defined for the sender. To learn how to fix this see: https://go.microsoft.com/fwlink/p/?linkid=2319303 Spf= Fail , Dkim= Fail , DMARC= None [DU5P191MB2406.EURP191.PROD.OUTLOOK.COM 2026-05-20T14:48:35.190Z 08DEB5D22BBE3A39] [PA7P264CA0308.FRAP264.PROD.OUTLOOK.COM 2026-05-20T14:48:35.199Z 08DEB61982916359] [AM4PEPF00025F96.EURPRD83.prod.outlook.com 2026-05-20T14:48:35.207Z 08DEB2A104B492DF]>'

Answer 3

EmilyS726 240.2K Independent Advisor

Hello

Can you share the rest of the error message? You only shared the part that it was rejected, but the rest of the information in that bounce email is critical to give an idea of why this happened.

M Douglas 0 Reputation points

2026-05-20T15:22:58.9433333+00:00

I just tried to send you a full copy of the error email but it was refused, something about code of conduct
EmilyS726 240.2K Reputation points Independent Advisor

2026-05-20T15:26:36.69+00:00

No worries. I got it. The issue is you shared the entire header with email addresses exposed, so it got removed to protect your privacy. I removed the header, which is not needed in this case. The error message is sufficient.

The dbmail.com domain you provided has SPF and DKIM configuration issues, hence they are rejected by Microsoft. Please let their support know, once corrected, their emails can be accepted typically within 24 hours. See Microsoft's announcement about SPF/DMARC/DKIM requirements here: https://techcommunity.microsoft.com/blog/microsoftdefenderforoffice365blog/strengthening-email-ecosystem-outlook%E2%80%99s-new-requirements-for-high%E2%80%90volume-senders/4399730
M Douglas 0 Reputation points

2026-05-20T15:28:16.56+00:00

The domain was taken over by Outlook some 15 yrs ago
M Douglas 0 Reputation points

2026-05-20T15:29:05.73+00:00

DBMAIL.COM domain
EmilyS726 240.2K Reputation points Independent Advisor

2026-05-20T15:31:57.17+00:00

Even if the email service is via Microsoft, it still requires the domain owner to set up SPF, DKIM and DMARC records. These are industry wide protocol these days, while they were not very common 15 years ago as spoofing threats were not as bad as they are now.

You said it was taken over by outlook 15 years ago, did you purchase this domain yourself, and with some Microsoft 365 family or personal subscription then?
M Douglas 0 Reputation points

2026-05-20T15:38:59.4133333+00:00

No, I just had this email adresse when emails were starting, the then owners of the domain were Darty Box , a company selling PCs around 1998 I think. Latter the domain was sold or given to Outlook or MSFT, I once tried to find the domain but was not successful.
M Douglas 0 Reputation points

2026-05-20T15:40:38.45+00:00

I just had a free subscription for this email adresse.
EmilyS726 240.2K Reputation points Independent Advisor

2026-05-20T15:57:53.91+00:00

Ok, I ran a public record check for this domain, and this is the result:

https://www.whois.com/whois/dbmail.com

The domain itself is not registered with Microsoft. However, its email service is currently hosted by Microsoft.

This is common and does not mean Microsoft owns or controls the domain. Think of it like a company registered in New York that outsources its legal department to a company in Chicago and its IT services to another company in Seattle. The headquarters still manages the official contracts and records to document these vendor relationships, even though the services are provided from elsewhere.

In the same way, a domain such as dbmail.com can be registered through CSC Corporate Domains, Inc., while the domain owner chooses to host email through Microsoft by setting up Microsoft MX records in their DNS. They could also host their website with a completely different provider.

For email to be trusted and compliant today, the domain owner needs to configure SPF, DKIM, and DMARC records in the DNS manager where the domain’s DNS is managed, through CSC Corporate Domains. These records act like authorization records. They tell recipient mail servers that Microsoft is allowed to send email on behalf of dbmail.com.

If the recipient server checks your incoming email and shows that SPF, DKIM, or DMARC failed, it means the recipient server could not verify that authorization. From the recipient’s point of view, it may look like Microsoft is sending mail for dbmail.com without the domain owner’s approval, which is how spoofing commonly works.

That is why these records are required now. If you are not the domain owner or DNS administrator, you cannot add or fix these records yourself. Since the domain is not registered with Microsoft, this part is outside Microsoft’s control.
EmilyS726 240.2K Reputation points Independent Advisor

2026-05-20T15:59:34.05+00:00

Forgot to mention, you can get in touch with domain owner hopefully via this form provided by CSC Corporate Domains https://domaincontact.cscglobal.com/contactholder/dbmail.com/registrant
M Douglas 0 Reputation points

2026-05-20T16:01:59.3066667+00:00

The answer is I guess, I don't know who the owner of the domain is and I can't find out how to contact them.

Why has it worked for twenty + yrs then suddenly stop for a few addresses, all for @gmail.com and @Outlook.com but not at others and I can receive all emails from both.
EmilyS726 240.2K Reputation points Independent Advisor

2026-05-20T16:09:52.26+00:00

I shared the contact form above so you can start there and hopefully locate the domain owner.

As I mentioned earlier, spoofing threats were not as serious years ago, but they have become much worse. Cybersecurity is constantly evolving, so policies, protocols, and technologies have to change to keep up.

The article I shared earlier explains Microsoft’s implementation phases. Microsoft actually gave custom domain senders a generous timeline before full enforcement. It started with softer handling, such as marking messages as unverified or sending them to spam, and then moved toward harder rejection.

Other email providers are making similar changes as well, but each provider follows its own timeline and uses its own threshold for what counts as a “high-volume sender.” Because of that, some inconsistency is normal. However, this is definitely an industry-wide direction, and email authentication requirements are only going to become stricter over time.
M Douglas 0 Reputation points

2026-05-20T16:18:44.0633333+00:00

I sent them a message and for now I received a conformation saying they will try to contact the domain but ...

If I don't get a reply is there any solution?
EmilyS726 240.2K Reputation points Independent Advisor

2026-05-20T16:29:57.98+00:00

If they cannot help you, then unfortunately there's nothing Microsoft can do over here. Like in the example I gave you, if your company in NY didn't properly authorize a contractor in Chicago to do the work on your behalf, the Chicago company cannot just go out to your clients and perform jobs on your behalf legally; your clients would be calling this Chicago company a scammer.

I am afraid you would have to troubleshoot with CSC here. If it cannot be resolved at all, I fear you would have to switch your email address.
M Douglas 0 Reputation points

2026-05-20T16:42:18.4133333+00:00

What can I do about all of the emails and folders that I have in this outlook adresse?
EmilyS726 240.2K Reputation points Independent Advisor

2026-05-20T16:52:04.09+00:00

How do you check your emails? If you check it via web browser, there's no export option. You can continue to sign in there and they are not going anywhere.

Or do you use email app like Classic Outlook? If so, you can go to Files > Import/Export to export everything out as .pst file.

Answer 4

M Douglas 0

Mine is an outlook adresse and emails sent to other outlook adresses are refused, how can this be fixed??

Your list doesn't explain how to fix the problem.

Is it an insurmountable problem for Outlook to fix??

Must I change my email adresse?

I only send a few emails per week.

0 comments

Answer 5

The error indicates that messages are being rejected by the receiving organization’s mail protection (in this case, a server at mail.protection.outlook.com). This is a delivery failure scenario similar to the Outlook.com “delivery failed” cases.

Common causes and actions based on the provided guidance:

Check the exact non‑delivery report (NDR)
- Open the bounce/undeliverable message and look for specific text such as:
  - “Host unknown or Domain lookup failed” → the recipient domain doesn’t exist.
  - “Mailbox full or Quota exceeded” → recipient’s mailbox is full.
  - “Mailbox not found / Invalid mailbox / User unknown / Mailbox unavailable” → address doesn’t exist or is temporarily unavailable.
  - “Message too large” → message exceeds size limits.
  - Errors mentioning “blocked”, “listed in”, or spam lists → your sending server/account is being treated as a spam source.
Validate recipient addresses
- Confirm each recipient’s email address is correct and current.
- Correct any typos in the domain (for example, gmail.com vs gmai.com).
Check for size or attachment issues
- If the message has large attachments, reduce the size or remove them and resend.
- For Outlook.com specifically, messages with attachments larger than 25 MB cannot be sent.
If the NDR mentions spam filters or blocklists
- The receiving server may have blocked the sending server or domain as a spam source.
- The guidance is to contact the support team for the recipient’s email provider and request that the account or domain be unblocked.
If the NDR indicates temporary server/resource issues
- Messages like “No adequate servers”, “Resources temporarily unavailable”, “Out of memory”, or “Connection timed out” are typically transient.
- Wait a short time and resend; in many cases the issue resolves on its own.
If using Outlook.com as the sending service
- Review the non‑delivery receipt reason text. Common reasons include invalid address, mailbox full, server issues, or spam filtering.
- If the address is correct but messages still fail, use the Outlook.com sender support channel referenced in the guidance.

If the problem persists across many domains and the NDR references blocking or spam lists, it is likely a reputation or block issue on the sending side that must be cleared by working with the relevant mail provider’s support.

References:

Share via

Emails are being returned as undeliverable

6 answers

Your answer