Whether you are a list member or the editor or the moderator, simply send the message to firstname.lastname@example.org.
Messages posted from the list editors will be automatically sent on with no approval required. If the list configuration settings are set to send=editor,hold,confirm then a confirmation message will be sent to that editor. This is for security to ensure that a hacker has not faked the sending address.
All other messages will be sent to either the first listed editor, for a basic edited list, or the list moderators, for a moderated list.
See the List Owner's Manual, section 2.13 Setting Up Lists for Specific Purposes for more detailed information.