Sending, receiving, and organizing email in Outlook on the web for business
Hi Bill,
Welcome to the Microsoft Q&A forum.
Based on your description, it appears that your outgoing email was blocked during the sending process.
To obtain a clearer understanding of the issue, please run a Message Trace for the most recently blocked email to determine whether it was blocked due to an anti-spam policy or by the recipient's mail system.
Please follow the steps below:
- Sign in to the Microsoft 365 Admin Center.
- Open the Exchange Admin Center.
- Navigate to Mail flow > Message trace.
- Search using the affected sender's and recipient's email addresses.
After completing the Message Trace, please share the results with me so that I can assist you more effectively.
You can refer to the following documentation: Trace an email message in Exchange Online | Microsoft Learn
Note: Please redact or blur any personal information before sharing the results to protect your privacy and personal data.
I look forward to your response.
If the answer is helpful, please click "Yes".
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