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We receive emails at a distribution group (email@example.com) from a post-only SMTP server. The from address of the mail message is on another domain (firstname.lastname@example.org). Sometimes the content of the message may be spam-like, but the server itself has SPF record at another-domain.com and is not blacklisted in any DNS BL. However, we never receive the messages sent from the SMTP server. They don't even appear in the Junk Mail folder. Messages sent from elsewhere are fine, and messages sent to another domain (eg, outlook.com) can be received (although sometimes appear in the Junk folder).
I tried to add the domain (another-domain.com) in the Safe Sender list, but seems to have no use.
If you are using Offic365 Plan E, you can use FOPE to setup the policy rule to ensure @anotherdomain.com is in safelist.If you are using Office365 Plan P, you can add the address in the safelist of mailbox level to bypass it.
We will provide the detail information later.
Thanks, Neo Zhu
situation, I would like to suggest you use Delivery Report to check whether
this email has been delivered to Office 365 by referring the link below:
If there are any
results or updates, please feel free to let me know.
To simplify the issue, I changed the settings (in the application) so the mails are delivered to email@example.com (instead of a distribution list) and firstname.lastname@example.org. When I received the mail at outlook.com, I search delivery reports for mails in "user" mailbox that came from email@example.com. There's no message.
A quick update:
I changed the settings again so the mail is being sent from a monitored account. I then receive a message saying that the SMTP server's IP is being blocked. The whole message is:
Diagnostic-Code: smtp;550 5.7.1 Service unavailable; Client host [smtp-server-ip] blocked using Blocklist 1, mail from IP banned; To request removal from this list please forward this message to firstname.lastname@example.org.
I used MX Toolbox and the SMTP server is not on any blacklist.
For a further
troubleshoot this issue, could you please provide us the whole NDR? To request
the NDR, I have sent a Private Message with a subject of <How to Adjust
Spam Settings?> to you.
To access the
-Go to the Your
details section on the right side of the community site.
-Click the subject
title of the response to read the message
How are things going? Do you need further assistance?
If there are any questions, please feel free to post.
It turned out that the IP of the SMTP server we are using was on a blacklist of Office 365. The IP has been removed from the list and everything's working now.