Category Archives: Bounce Backs

Blocking Non-Delivery Report (NDR) spam with HTML Attachments

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We have posted a few helpful hints for users that are experiencing problems with Password Reset requests, UPS, Western Union, Youtube and other forms of spam. However, it looks like the spammers are altering the message to adapt to the changes that Postini and other vendors are making, so more updates to the filters are expected.
We are recommending that a temporary custom attachment filter to block all messages with a .html attachment is enabled within Postini. NOTE: If this filter is applied, it will block any legitimate message with that type of attachment. See below for the steps to enable the filter and the recommended settings:

Attachment Manager Filter Steps
  1. Access the customer’s Postini User Org and enable the Inbound Attachment Manager.
  2. To build a custom filter for blocking .html attachments, select Filter and follow the image below:

  3. We highly recommend enabling ‘Scan inside compressed file types’ and ‘Enable binary scanning’ as this may also help with any future evolutions.
  4. Be sure to add ‘html’ under 2. Custom Filter Types to either User Quarantine (in case of false positives) or under Quarantine Redirect.
  5. Click Save and the filter is applied.

MxToolbox has partnered with WebRoot to offer Web Filtering to protect your network from attacks through the web browser. For more details on the protection that this program can offer, go here.

What does the Bounce Message – “Unable to Relay” Mean?

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If your customers are receiving an error message like below, there are 2 settings that may need to be adjusted.

‘name@domain.com’ on 9/15/2006 11:11 AM
550 5.7.1 Unable to relay for name@domain.com

Configure your Exchange Server to accept mail anonymously for your domain

The directions below are for Exchange 2007, but most mail servers should have similar settings.
  1. Please confirm that your Send Connector has Anonymous Users allowed under Permission Groups.
  2. Open your Exchange Management Console and access Server Configuration > Hub Transport > Receive Connectors

  3. Right Click on the Default (or any other Receive Connector your company uses) and choose Properties.
  4. Select the Permission Groups tab and ensure that Anonymous Users is checked.

    NOTE: This does NOT allow anonymous users to send mail through your server, this would configure the server as an Open Relay; that would be bad. This allows anonymous users to  have access to the Receive Connector so they can send mail addressed to your domain(s).
Configure your Email Client to authenticate when it connects to your SMTP server
To resolve this issue please adjust their email client to require ‘My Outgoing Server SMTP Requires Authentication’. The directions below are for Outlook 2007, but most mail clients should have similar settings.
  1. Open Outlook
  2. Go to Tools > Email Account > Change
  3. Click More Settings > Select Outgoing Server tab and ensure that check box next to My Outgoing Server SMTP Requires authentication is enabled.
  4. Click Ok and Next and Finish.