In Thunderbird

• Go to the “Tools” menu and choose “Options…”
• Go the the “Privacy” section and choose the “Security” tab
• Click “View Certificates”
• Choose the “Authorities” tab and click “Import”
• In the filename field type in “http://www.cementhorizon.com/cacert.pem”
• When the “Downloading Certificate” window pops up :
  • check “Trust this CA to identify Web Sites”
  • check “Trust this CA to identify email users”
  • check “Trust this CA to identify software developers”
• Then click “ok”