Outgoing emails falsely marked as SPAM / Phishing emails by Outlook servers

[ExpertInstitute]

Since 10/26/21 our organization has been experiencing widespread email deliverability issues with Microsoft / Outlook clients. These are legitimate / wanted emails sent to opted-in users - existing clients who are expecting our emails. These emails are falsely being quarantined / sent to spam, or even rejected in some cases, specifically by Microsoft 365 / Outlook receiving servers. 

We've been thoroughly testing for the past 6 weeks and it appears to be specific to our domain and not related to our email sending platforms or IPs. This issue has been persisting across our entire organization. Our DKIM / SPF records are all implemented correctly. We're using Dmarcian, HetrixTools to monitor / confirm these DNS settings. We have also retained two email deliverability consultants, who have checked our domain settings. They've also confirmed that they believe this is an internal false flag on Microsoft's side. 

For the past 6 weeks, we have been in touch with Outlook Deliverability Team and countless support staff. The issue has been escalated and we have provided them with email samples of quarantined / rejected email headers, but still the issue remains prevalent and unresolved. This issue is severely impacting our business, as our clients are unable to receive emails / work product for which they have already paid.

We are desperate and seeking assistance / guidance from someone on the Microsoft Outlook Team, who can kindly escalate this issue, and advise us on next steps to delist our domain from their internal blacklists. Again, this issue is impacting existing client relationships. Clients who are not receiving wanted emails in order to conduct business.

[#2]

@ExpertInstitute 

Hello, this documentation should be helpful

Report false positives and false negatives in Outlook - Office 365 | Microsoft Docs

Manage your allows in the Tenant Allow/Block List - Office 365 | Microsoft Docs

Report spam, non-spam, and phishing messages to Microsoft - Office 365 | Microsoft Docs

Manage accepted domains in Exchange Online | Microsoft Docs

[#3]

Thanks for the reply. But unfortunately, none of these resources are necessarily relevant to our issue. We are the sending domain, not the receiving domain.

It is our end user clients who are using Outlook and unable to receive emails from us containing work product. These are legitimate / wanted emails that are falsely being flagged as spam by their Outlook client inboxes.

[#4]

https://docs.microsoft.com/en-us/microsoft-365/security/office-365-security/use-the-delist-portal-to...

[#5]

Thanks again, but unfortunately this also does not apply. Because we are using Shared IPs from services like Gmail, Hubspot, or SendGrid. We've also determined that the issue is not IP related, but domain related.

[#6]

@ExpertInstitute 

I am having what sounds like the same issue.  Did you ever figure it out?

[#7]

Exact same issue here. Hoping for an update from @ExpertInstitute as well