Azure IP blocked from sending mail to Microsoft domains

Robert Micallef 6 Reputation points
2023-01-09T11:43:29.987+00:00

We are trying to send mails to our clients from a mail server which we migrated to Azure and we got the following error:
552 Mail rejected by the processing module: 5.7.1 Unfortunately. messages from [AZURE-OWNED-IP] weren't sent. Please contact your Internet service provider since part of their network is on our block list (S3140). You can also refer your provider to http://mail.live.corramaiVtroubleshooting.asiodterrors. [13N8NAM12F1110.eop-nam12.prod.protection.outlook.com]
This is a mail server we recently moved to Azure. SPF, DMARC etc are all good. We never had issues before it was migrated. I tried requesting to be unblocked by sending and email to delist@messaging.microsoft.com and I got the response that the Azure owned IP is "Not qualified for mitigation". I can't believe Microsoft are blocking themselves. They didn't even say why I was blocked and the error says that Part of the network so it looks like they blocked a whole subnet (owned by them).
Does anyone know how I can please reach someone to get this sorted please?

Microsoft Exchange Online
Microsoft Exchange Online Management
Microsoft Exchange Online Management
Microsoft Exchange Online: A Microsoft email and calendaring hosted service.Management: The act or process of organizing, handling, directing or controlling something.
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  1. Manu Philip 17,186 Reputation points MVP
    2023-01-09T13:32:53.07+00:00

    Microsoft maintains their own internal blacklists, which are used to reject emails coming from specific IP addresses. Any IPs listed on the Spamhaus blacklist are also blacklisted by Microsoft

    Please also ensure your emails comply with the Microsoft policies, practices and guidelines found on their website: https://postmaster.live.com/pm/policies.aspx

    Once you have done that, you can follow the instructions below to get your IP delisted.

    To delist IPs from this blacklist, please fill out the following forms:
    Outlook > http://go.microsoft.com/fwlink/?LinkID=614866&clcid
    Office 365 > https://sender.office.com/

    --please don't forget to upvote and Accept as answer if the reply is helpful--

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  2. Robert Micallef 6 Reputation points
    2023-01-09T18:01:08.197+00:00

    We already tried those steps and we fully comply with all sending requirements. We have opened another case maybe this gets us somewhere.