$ldap->modify($dn, add => [ homeMDB  => 
 'CN=Mailbox Store (DOMAIN),CN=First Storage 
 Group,CN=InformationStore,CN=DOMAIN,CN=Servers,CN=First 
 Administrative Group,CN=Administrative Groups,CN=DOMAIN,CN=Microsoft 
 Exchange,CN=Services,CN=Configuration,DC=DOMAIN,DC=com,DC=au']);

$ldap->modify($dn, add => [ mDBUseDefaults => 'TRUE']);

$ldap->modify($dn, add => [ msExchHomeServerName => '/o=DOMAIN/ou=First 
 Administrative Group/cn=Configuration/cn=Servers/cn=DOMAIN']);

$ldap->modify($dn, add => [ mail => email address ]);

$ldap->modify($dn, add => [ mailnickname => Nickname ]);

$ldap->modify($dn, add => [ targetaddress => "SMTP:email address" ]);