I make a directory assistance with a LDAP connection document.
In the property "Attribute to be used as notes Distinguished name" I put mail.
So in Notes database I put email address on ACL and Reader/Author field and it's work fine.
But when I put the mail address in the Notes group it doesn't work.
I make the test with the CN and it's work.
I don't know if there are a specific syntax to put mail address(LDAP) on Notes Groups.