Someone

# defines if the particular DL can be accessed from outside or not
attributetype ( 1.3.6.1.4.1.4203.666.1.11
        NAME 'externalAccess'
        EQUALITY booleanMatch
        SYNTAX 1.3.6.1.4.1.1466.115.121.1.7 
)

objectclass ( 1.3.6.1.4.1.4203.666.1.100
  NAME 'DlGroupOfNames'       
  DESC 'Distribution list of rfc822 attributes, and external access auth'
  SUP groupOfNames AUXILIARY
  MAY ( mail $ externalAccess ) 
)