mj-column-border-issue-466.mjml

<mjml>
  <mj-body>
    <mj-section>
      <mj-column padding-left="10px" border="3px solid black">
        <mj-text>Hello World</mj-text>
      </mj-column>
    </mj-section>
  </mj-body>
</mjml>