Remote Server returned '550 5.7.501 Access denied, spam abuse detected.

Question

&nbsp;Anyone else receiving "Remote Server returned '550 5.7.501 Access denied, spam abuse detected." when attempting to send from @&lt;O365subdomain&gt;.onmicrosoft.com?&nbsp;Found various discussions that mention MS Engineers 'delisting' domain to resolve the issue?http://answers.microsoft.com/en-us/msoffice/forum/msoffice_outlook/remote-server-returned-550-57501-access-denied/23b2794d-ddc2-4e4d-a4b7-ee1f136a300a?page=2http://answers.microsoft.com/en-us/msoffice/forum/msoffice_outlook-mso_win10/cant-respond-to-emails-anymore-receiving-this/cf29cbfd-3e7b-48d3-a186-8436b5ee35f9http://answers.microsoft.com/en-us/msoffice/forum/msoffice_outlook/remote-server-returned-550-57501-access-denied/7d6df30b-a185-4c69-95b7-2c94537127ee

victor_ungureanu · Answer

Yes, this is something usual when sending from onmicrosoft.com and when the originating IP is from specific network classes.
&nbsp;
You can send from a vanity domain, or send from another network that is not blacklisted, or you can open a service request to Microsoft Support and give them a complete NDR.

anthony obi · Answer

Thanks Victor.&nbsp;Attempting to send from https://outlook.office.com so assuming no way of affecting/changing the originating IP network classes etc?&nbsp;Will try applying custom domain (vanity domain) to O365 tenancy and try resending.(Failing that, service request to Microsoft Support as suggested)&nbsp;Thanks

victor_ungureanu · Answer

Changing the primary SMTP to a vanity domain will solve this issue for sure :)

anthony obi · Answer

Also found list of NDR Codes from O365https://support.office.com/en-gb/article/Email-non-delivery-reports-in-Office-365-51daa6b9-2e35-49c4-a0c9-df85bf8533c3&nbsp;5.7.501Access denied, spam abuse detectedThe sending account has been banned due to detected spam activity.For details, see https://support.office.com/en-gb/article/Fix-email-delivery-issues-for-error-code-451-57500699-ASxxx-in-Office-365-51356082-9fef-4639-a18a-fc7c5beae0c8.Verify that any account issues have been resolved, and reset its credentials. To restore this account’s ability to send mail, contact support through your regular channel.&nbsp;https://support.office.com/en-gb/article/Fix-email-delivery-issues-for-error-code-451-5-7-500-699-ASxxx-in-Office-365-51356082-9fef-4639-a18a-fc7c5beae0c8

victor_ungureanu · Answer

When sending from the onmicrosoft.com domain the cause of the NDR is most likely not that "The sending account has been banned due to detected spam activity."
&nbsp;
As I said before, sending from the onmicrosoft.com domain is blocked when the originating IP is part of specific IP classes as a measure of preventing spammers to create free trial tenants and sending spam using them&nbsp;:)

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Remote Server returned '550 5.7.501 Access denied, spam abuse detected.

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