This rule will change the message icon to a "Lock" icon, protect it and set the expiry to never.

Header and Conditions Tab

  1. Name: Protect Message
  2. When: Run Manually
  3. If: All > Always

Actions Tab Criteria 1

Set the First action as

  1. Turn Protection
  2. On

Actions Tab Criteria 2

  1. Click on the + icon to add a second criteria
  2. Choose Set Icon
  3. Select the Padlock icon

Actions Tab Criteria 3

  1. Click on the + icon to add a third criteria
  2. Choose Set expiry period
  3. Choose Never

Command Tab

  1. Check Add to toolbar
  2. Command icon: Select the Padlock icon by <Control> or <Option> clicking on the icon field
  3. Command name: Enter Protect Message
  4. Check Show Name
  5. Tooltip text: Enter "Protect message and clear expiry"
  6. Command enabled: Choose Documents Selected

Save the rule