Microsoft’s Exchange & @hotmail.com / @outlook.com domains Spam problem.

Question

Microsoft’s Exchange & @hotmail.com / @outlook.com domains Spam problem.

Goran Salamunićcar 20

The email sent from a Microsoft’s Windows virtual machine using an application written in Microsoft’s Visual Studio and using the Microsoft’s SMTP server received at @yahoo.com and @googlemail.com, but it didn't even end up in the Junk Email at Microsoft’s email addresses @hotmail.com and @outlook.com.

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Answer 1

Anonymous

Hello, @Goran Salamunićcar,

Welcome to the Microsoft Q&A platform!

According to your description, your test email can be found at @yahoo.com and @googlemail.com but not at Microsoft’s email addresses @hotmail.com and @outlook.com.

To solve this issue, the first thing you should do is to check for any non-delivery reports (NDRs) that might provide more information about why the emails were not delivered. These reports can indicate issues like incorrect email addresses, server problems, or policy violations. If you do not receive any NDRs, please use the message trace feature in the Exchange admin center to track the status of the emails. This can help determine if the emails were blocked, delayed, or failed to deliver.

Reference documents:

1.Email non-delivery report (NDR) and SMTP errors in Exchange Online - Exchange | Microsoft Learn

2.Find and fix email delivery issues as a Microsoft 365 for business admin - Exchange | Microsoft Learn

Besides, here are some other steps you can take to troubleshoot this problem:

1.Check the SMTP Server Configuration: Ensure that your SMTP server settings are correctly configured. Sometimes, misconfigurations can lead to delivery issues.

2.Review Email Filtering Settings: Microsoft email services have robust spam and junk email filters. It's possible that your emails are being filtered out before they reach the Junk Email folder. You can review and adjust these settings in the recipient's email account.

3.Check for Blocked Senders: Verify that your sending email address or domain is not on a blocklist. Microsoft email services might block emails from certain addresses or domains if they are flagged as spam.

4.Review SMTP Server Logs: Check the logs on the SMTP server to see if there are any errors or bounces when sending to Hotmail or Outlook addresses.

5.Spam Filtering: Exchange Online has robust spam filtering mechanisms that might block emails from certain senders. Ensure that the sender's email address is not on any block lists and consider adding it to the safe senders list.

Also, a document to help you with email delivery issues is here for your reference: Find and fix email delivery issues as a Microsoft 365 for business admin - Exchange | Microsoft Learn.

Should you need more help on this, you can feel free to post back.

If the answer is helpful, please click on “Accept answer” as it could help other members of the Microsoft Q&A community who have similar questions and are looking for solutions.

Thank you for your support and understanding.

Best Wishes,

Alex Zhang

Goran Salamunićcar 20 Reputation points

2025-02-02T20:43:57.0833333+00:00
Hello Alex Zhang,

Thank you for your detailed response. That is very helpful and a step forward, but unfortunately it did not solve our problem. If anything in the following text is incorrect, please feel free to correct me.

In our association, some members complained that they had not received their membership fee payment details for 2025 by email. Analysis led to the conclusion that these were primarily members which use the @hotmail.com and @outlook.com domains from Microsoft. I can send you that analysis by email or describe it further, if you wish.

We don't use Microsoft Exchange Server, but as I understand it, that's the mail server used for the @hotmail.com and @outlook.com domains. It is possible that Exchange is also used as a mail server for some of the remaining domains with which we have problems, so if we solve it, it can potentially help with that as well.

It was very inconvenient for us that we did not receive any Non-Delivery Reports (NDRs or just "bounce") that could provide more information as to why the emails were not delivered. So we were sure that we had sent all the members information about the payment of the membership fee for the year 2025, and we realized that we had a problem only after some started complaining that they did not receive our invoice by e-mail. The email addresses are from our member database and are correct. We have not noticed any server issues or policy violations. We cannot use the message tracking feature in the Exchange administration center because it is not about our servers, but about servers where our members have email addresses. But if you want us to do this analysis on the mail server that runs @hotmail.com and @outlook.com, please let me know and I will be more than happy to find together with you where the problem is.

The following is a response to other suggested steps to resolve this issue:

The SMTP server configuration is fine, most of our members received emails as well as I personally at @yahoo.com and @gmail.com addresses.

I can't view the email filtering settings because this is not our Exchange, but the Exchange used for the @hotmail.com and @outlook.com domains. I don't believe we have access to these settings for your server. I tried adding our domain and sender email address to one @hotmail.com user and one @outlook.com user safelist, but that didn't help. So I think you're right that our email is being filtered by your Exchange Server before it reaches the Inbox or the Junk Email folder at @hotmail.com and @outlook.com.

As for checking blocked senders, we are the only user on our private Windows virtual machine and the only application I wrote sends only legitimate email, so I assume we could only be on some block list if we ended up there through some mistake or abuse.

Reviewing the SMTP server logs was a big step forward, more information is provided as follows.

As for Spam filtering, on the two email addresses I opened at @hotmail.com and @outlook.com for analysis purposes, my address is certainly not on the block list, and adding my email and/or domain to the safe senders list did not help.

Regarding the SMTP server records, in C:\inetpub\mailroot\Badmail, there is the following pattern in files with the BDR/BDP/BAD extensions, such as:

0019f053412070420240000029A.BDR: Unable to deliver this message because the follow error was encountered: "This message is a delivery status notification that cannot be delivered.". The specific error code was 0xC00402C7.

0019f053412070420240000029A.BDP: PTR record setup, or the corresponding forward DNS entry does not match the sending IP. As a policy, Gmail does not accept messages from IPs with missing PTR records.

0019f053412070420240000029A.BAD: Final-Recipient: rfc822;.@outlook.com Action: failed Status: 5.7.1 Diagnostic-Code: smtp;550 5.7.1 Service unavailable, Client host [...] blocked using Spamhaus.

There are only two possibilities: (1) Microsoft's Exchange reports us to Spamhaus and then does not accept our emails; and (2) someone else reports us to Spamhaus (potentially for the same e-mail that it puts not in Spam but in Inbox) and then Microsoft's Exchange doesn't accept our emails in either the Inbox or the Junk Email.

For the sake of analysis, I clicked on the Spamhaus report to remove the IP address of our server from the blocklist, and after that test emails arrived to the address I opened at @hotmail.com and the address I opened at @outlook.com. This confirmed that this is why our emails do not reach users who use the domains @hotmail.com and @outlook.com. But with the first subsequent sending of emails by our application, I again found ourselves on the list blocked by Spamhaus, so the problem has not been solved yet. We also send our emails automatically every day at 07:00:00 UTC, after we receive during the night the bank statement for the previous day, to inform members that we have processed their payments as membership fees.

We have purchased a license for EmailArchitect to use in conjunction with Microsoft's SMTP server so that our legitimate email is not misclassified as Spam. But it seems that in addition our ISP has to set up the missing PTR (reverse DNS) for the IP address of our Microsoft Windows virtual machine.

Should I proceed in that way, should we do an analysis together to determine what exactly is coming if you are as well interested, or something else?

Thank you @Alex Zhang very much in advance.
Anonymous

2025-02-04T05:51:50.55+00:00

Hello, @Goran Salamunićcar,

Thank you for your detailed reply. I am quite willing to analyze the issue with you.

Based on what you’ve described, the core issue appears to be with your sending IP’s reputation, particularly since a manual Spamhaus removal temporarily restored deliverability, and the absence of a PTR record is likely contributing to this problem. Setting up a proper reverse DNS (PTR) record for your server’s IP is a critical first step, as many receiving servers require that the sending IP correctly resolve to a hostname, which should in turn resolve back to the IP address. Additionally, verifying that SPF, DKIM, and DMARC records are correctly configured will further enhance your email legitimacy and reputation.

Beyond technical configurations, it’s worth analyzing your email headers and delivery logs—especially for the bounced or blocked messages—to identify if there are any additional contributing factors, such as patterns in email content or the sending schedule, that might trigger spam filters.

Let me know if you’d like to dive deeper into any of these areas or if you have particular logs or specifics you’d like help analyzing.

Best Wishes,

Alex Zhang
Goran Salamunićcar 20 Reputation points

2025-03-16T18:54:42.5533333+00:00

Hello, @Anonymous ,

Thank you very much for being quite willing to analyze the issue with me.

We set up a proper reverse DNS (PTR) record for our server’s IP, the HELO which is now a fully qualified domain name (e.g. "hostname.example.com"), and email address for a DMARC reports.

According to the delivery records and the BCC used, we achieved deliverability on the @hotmail.com / @outlook.com domains.

However, the logs indicate that there was something more to it. Other administrators in our association didn't believe it at first, but changed their minds after seeing the logs and the analysis I did. They were as well surprised by what it turned out to be.

I would be quite keen to dive deeper into these unexpected logs and findings with you regarding these specifics. I you are fine with an online meeting as well that would be just great.

Thank you @Alex Zhang very much in advance, I sincerely look forward to your response.

Best Regards, Goran.Salamuniccar at outlook.com.

Answer 2

asakra mudege 0

查看 SMTP 服务器日志：检查 SMTP 服务器上的日志，查看向 Hotmail 或 Outlook 地址发送邮件时是否有任何错误或退回。

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Microsoft’s Exchange & @hotmail.com / @outlook.com domains Spam problem.

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