AD configurations can differ a bit. MY distro lists are accessible via
LDAP:
But what do you mean by "don't resemble"? Completely wrong, or not in the format you think they should be in?
EDIT:
Howveer, IF your groups and distribution lists are all sitting in the same OU, you can distinguish them using the "groupType" property.
If the groupType is
2147483648 (0x80000000) (according to MS) or
-2147483646 (according to my AD), it is a security group. Any other number (1,2,4,8,16, or 32) makes it a distro list.