This element is required and indicates the type
of organization provided in the OrgName element. It is one of PLA, Group, or
GroupMember. PLA indicates the value is an individual recipient identified by
its plain language address. Group indicates the value is a group name
identifying multiple recipients by their membership in the group. GroupMember
indicates the value is the plain language address of an address group member.
GroupMember should only be used when the recipient list also includes an
OrgType of Group.