Event invites marked as spam within Outlook instance

Question

I am using the Graph API to create an event and then using the Update Event API to invite attendees to the event. These attendees are from the same Outlook tenant as the organizer, but attendees are not receiving emails of the invitation because they are marked as spam.

This is a new instance that has been spun up, only existing for about a week. Here is the warning I have received:

Remote server returned '550 5.7.501 Service unavailable. Spam abuse detected from IP range.

I am surprised that emails sent from Outlook are marked as spam even within the same tenant.

Is there anything I can do to mitigate this?

Answer 1

Hi @pklong ，

Remote server returned '550 5.7.501 Service unavailable. Spam abuse detected from IP range.

Are you using the onmicrosoft.com domain name? Which is often used for testing, causing the recipient server's policy to block your IP address range. You can check suggestion provided in our official article Fix email delivery issues for error code 451 4.7.500-699 (ASxxx) in Exchange Online | Microsoft Docs.

To fix this issue your Tenant needs to be added to a sending exclusion for 60 days to allow them to use blocked IPs whilst they still have a new/trial license.

You can also submit a service request to Microsoft Support and provide a complete Non-Delivery Report (NDR). The Microsoft support team can help you remove your IP address from the blocked senders list.

(Please note that it may take up to 24 hours to remove all restrictions from the IP address)

---

If the answer is helpful, please click "Accept Answer" and kindly upvote it. If you have further questions about this answer, please click "Comment".

Answer 2

Hello,

Please refer to the link below for Creating safe sender list.

https://learn.microsoft.com/en-us/microsoft-365/security/office-365-security/create-safe-sender-lists-in-office-365?view=o365-worldwide

If the answer is helpful, please click "Accept Answer" and kindly upvote it. If you have further questions about this answer, please click "Comment".