Send & Receive Issues

Fix Printer Scans Blocked by Microsoft 365 Email Policy (Error 550)

John Wilson Sep 28, 2026 869 views

Question details

Scanned documents sent from a university printer to a personal email address are being rejected.

How to Fix Printer Scans Blocked by Microsoft 365 Email Policy

Product: Microsoft 365
Device & OS: not provided
Scenario: A user is attempting to send scanned documents from an institutional printer directly to a personal email address.
Observed behavior: The emails are rejected with SMTP error 550 5.7.360. The messages do not appear in the Microsoft 365 message trace, quarantine, or alerts, indicating they may be blocked by an outbound filter like Mimecast.

Before you start

Confirm the exact SMTP error code received (e.g., 550 5.7.360) and verify if your organization uses a third-party outbound mail filtering service such as Mimecast before troubleshooting Microsoft 365 settings.

Solution 1Recommended

Contact Your Organization's Mail Administrator

Since the emails do not appear in Microsoft 365's message trace, they are likely being blocked by a third-party outbound mail system (like Mimecast) before reaching Microsoft's servers.

Institutions often employ secondary security layers for outbound mail. When an email from a local printer is dropped by these external systems, it won't generate logs in your standard Microsoft 365 environment.

Report the issue

Provide your IT support or mail administrator with the specific SMTP error 550 5.7.360 and the timestamp of the failed scan.

Request log review

Ask the administrator to check outbound mail-flow logs and third-party filtering logs, specifically looking at systems like Mimecast.

Update permitted senders

Request that your email address or the printer's sending address be added to the institution's permitted senders list (allowlist).

Test the scan

Once the administrator confirms the allowlist update, attempt to scan and send a document from the printer to your email address again.

Allowlisting success: Being added to the permitted senders list in the outbound filtering system resolves this specific blockage for most institutional networks.

Solution 2

Open a Microsoft 365 Service Request

If local third-party logs do not reveal the drop, a Global Administrator must engage Microsoft Support to investigate backend routing and hidden mail-flow rules.

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Frequently Asked Questions

What does SMTP error 550 5.7.360 mean?

This error code typically indicates that an email or its attachment was blocked by an outbound mail flow rule, anti-spam policy, or a third-party filtering service (like Mimecast) before it could be delivered to the recipient.

Why aren't my blocked printer scans showing up in Microsoft 365 Message Trace?

If the emails are being intercepted and blocked by a third-party outbound filtering system deployed by your institution before they fully process through the Microsoft 365 routing environment, they will not generate a record in the standard Message Trace or trigger quarantine alerts.

Can I fix error 550 5.7.360 myself as an end user?

Generally, no. This error requires an organization's IT department, mail administrator, or a Microsoft 365 Global Administrator to check backend mail-flow logs, adjust outbound anti-spam policies, or add your address to a permitted senders allowlist.

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