Approximately one week ago, we began experiencing issues with our Microsoft Outlook email system. Messages were being unexpectedly removed from user mail folders and placed into quarantine, requiring manual release.
We engaged Microsoft Support, who advised implementing specific transport rules and policies, and verifying that DKIM was correctly configured. DKIM has since been validated and appears to be functioning correctly.
However, the issue persisted. Upon further investigation with Microsoft, we were informed that the URL contained in our email signature was being flagged by Microsoft Defender as potential malware. We removed the URL from all signatures and submitted it to Microsoft Defender for review, which has now been completed and marked as clean.
Despite this, we continue to experience the following problems:
Outgoing emails may not always reach recipients (some recipients report not receiving messages).
Inbound emails from customers are sometimes not delivered to our mailboxes.
There is ongoing uncertainty regarding message delivery and filtering within our Microsoft 365 environment.
We are seeking an experienced Microsoft 365 / Exchange Online / Defender for Office 365 specialist to:
Diagnose and resolve the underlying mail flow and filtering issues.
Review and verify our domain authentication setup (SPF, DKIM, DMARC).
Audit existing mail flow rules, security policies, and quarantine settings.
Ensure that legitimate email traffic (both inbound and outbound) is delivered reliably and not flagged or quarantined incorrectly.
Please include details of your experience with Microsoft 365 mail flow, Defender policies, and domain authentication troubleshooting, along with your proposed approach for identifying and resolving these issues.
Skills Required:
Microsoft 365 / Office 365 Administration
Exchange Online / Outlook Mail Flow Troubleshooting
Microsoft Defender for Office 365 / Security & Compliance
SPF, DKIM, DMARC configuration and troubleshooting
Transport rules and mail flow policies
Email deliverability analysis and troubleshooting.
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