mjml-ecm-head-preview v4.4.0-ecm-18

mjml-preview

This tag allows you to set the preview that will be displayed in the inbox of the recipient.

<mjml>
 <mj-head>
   <mj-preview>Hello MJML</mj-preview>
 </mj-head>
 <mj-body>
   <mj-section>
     <mj-column>
       <mj-text>
         Hello World!           
       </mj-text>
     </mj-column>
   </mj-section>
 </mj-body>
</mjml>

mj-preview doesn't support any attribute.