Undeliverable for Manual spam flagging or Not Spam flagging

I have Trend Micro Maximum Security (Version 17.8, although this problem has occurred for a while) on Windows 10, running Outlook as part of Microsoft Office Professional Plus 2021; that is, desktop, not Office 365.

Trend detects some spam itself - with some false positives too - and sends emails to the Spam Folder.

When I manually Flag spam from the Inbox, I get a message back the next time Outlook polls. Something like this:
From    System Administrator     No email information
To      Me                       No email information
Subject Undeliverable: FW: Tax Lien List
Your message did not reach some or all of the intended recipients.

      Subject:     FW: Tax Lien List
      Sent:  12/19/2024 9:08 AM

The following recipient(s) cannot be reached:

      spam@cs.trendmicro.com on 12/19/2024 9:08 AM
            550 extension.        Apparently this is the error message - blocking this message at space@cs.trendmicro.com  
 

Following a similar process for a false positive generates almost the same result - but for false@cs.trendmicro.com
There are no Email headers visible. This isn't just an Outlook quirk - it's the messages coming in this way.

I wondered if the problem was changed receiving email addresses at cs.trendmicro.com, in which case what are the correct addresses, and how could I change them. But that doesn't seem to be it. Composing and sending Manual emails to the two addresses hasn't generated the Undeliverable responses.

What's going on? Is there a Hot Fix?  Coming?
Thanks, 
Mike                    

Hi Mike,

The undeliverable responses you're receiving when manually flagging spam or false positives are likely due to a misconfiguration or outdated feature in your Trend Micro Maximum Security setup. Our Antispam Toolbar is designed to automatically filter unwanted and fraudulent messages into a Spam Mail folder, without requiring manual reporting to specific email addresses.

To address this issue, please follow these steps:

1. Ensure you're using the latest version of Trend Micro Antispam Toolbar:

   • Make sure your Trend Micro Maximum Security software is up to date. You can check for updates within the application.

2. Check if the Antispam Toolbar is properly enabled in your Outlook settings:

   • Open Outlook.
   • Go to the "File" tab and select "Options."
   • Click on "Add-ins."
   • Ensure that the Trend Micro Antispam Toolbar is listed and enabled in the "Active Application Add-ins" section.

3. Adjust the Spam Filter settings to optimize detection:

   • Open Outlook and click the Trend Micro icon.
   • Select "Settings."
   • Go to the "Spam Filter" tab.
   • Adjust the "Spam Email Filter Strength" slider (Medium is recommended for a balance between detection and false positives).

If the problem persists after these steps, it may require further investigation by our support team. Please contact our support team for additional assistance.