Send & Receive Issues

Fix Sophos Email Alerts Not Arriving in Exchange Online

Maira Mehtab Sep 22, 2026 869 views

Question details

The user needs to troubleshoot an issue where automated firewall alerts from Sophos are not being received in a Microsoft Exchange Online mailbox, even though other regular emails are arriving normally.

Product: Microsoft Exchange Online
Device & OS: not provided
Scenario: Receiving automated system alerts from a Sophos firewall via email.
Observed behavior: Sophos email alerts are entirely missing from the Exchange Online inbox, while all other standard emails continue to arrive without any problems.

Before you start

Before beginning, verify that your Sophos firewall has an active internet connection and that the sender email address configured on the device is spelled correctly.

Solution 1Recommended

Check Exchange Mail Flow Rules, Quarantine, and Junk Settings

Verify if Microsoft 365 security features are actively filtering, redirecting, or blocking the automated alerts sent from the Sophos firewall.

Exchange Online often flags automated emails from hardware devices as spam or phishing attempts due to strict default security policies.

Run a Message Trace

Log into the Exchange Admin Center, navigate to 'Mail flow', and select 'Message trace'. Run a trace using the Sophos sender email address to see if Microsoft 365 received the message and where it was routed.

Review Microsoft 365 Defender Quarantine

Open the Microsoft 365 Defender portal, go to 'Email & collaboration', and select 'Review' > 'Quarantine' to check if the Sophos alerts were intercepted by security filters.

Check Local Junk Email Folders

Ask the affected user to open Microsoft Outlook and check their 'Junk Email' folder to ensure the alerts were not locally filtered by the email client.

Whitelist Sophos IPs: If alerts are being quarantined, consider adding the Sophos firewall's external IP address to your Exchange Online allowed senders or connection filter list.

Solution 2

Verify Sophos SMTP Authentication Configuration

Ensure the Sophos firewall is correctly configured to authenticate with Exchange Online's SMTP servers.

Solution 3

Reset Microsoft 365 Authentication Methods

Address account lockouts or authentication failures that are preventing the Sophos account from sending outgoing emails.

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Frequently Asked Questions

Why are only my Sophos alerts missing but other emails arrive normally?

Automated emails generated by hardware devices often lack certain headers or authentication records (like strict SPF/DKIM alignment), causing Exchange Online's spam filters to quarantine or drop them, while regular user emails pass through easily.

How do I run a message trace in Microsoft 365 for Sophos emails?

Log into the Exchange Admin Center, navigate to Mail flow > Message trace. Enter the sending email address configured on your Sophos device in the 'Senders' field and execute the search to view the delivery status.

What port should the Sophos firewall use for Exchange Online SMTP?

When connecting to smtp.office365.com, you should configure your Sophos firewall to use port 587 with STARTTLS encryption enabled to successfully authenticate and send alerts.

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