How do we add email classification or Sensitivity comparable to Outlook onto mail command on Linux

How do we add email classification onto mail command on Linux? I'm currently using the following command: mail -s "$(echo - e " Test\From:abc\nContent-Type: text/html")" -S -smtp="SMTP relay server" mailbox edit: If I interpret the original poster's question correctly this would only be for outgoing mail and be similar to Microsoft Outlook which has a **Sensitivity** drop down with choices like unrestricted or third party proprietary TTPI where that syntax seems to just be appended to the mail subject line. Is there a way to make this happen in Linux like it does in Microsoft Outlook? google outlook email sensitivity and look at related pics to get an idea. example: https://www.vumc.org/it/vumc-it-blog/use-sensitivity-labels-outlook-protect-email