This is especially important if you suspect the message contains a virus.
Instructions cover Thunderbird or Netscape email.
(Look inAccount configs>Server SettingsandMessage Storageto see how yours is set up.)

go for the message you want to delete in the message list (without opening it).
Hold down theShiftkey while pressingDel.
In the Confirm Deletion box, pressDelete.
Your message will be deleted immediately, and no copy will be saved to the Trash.