For multi domains support remove SOGoUserSources and change it to:

    domains = {
           MyDomain.ltd = {
               SOGoMailDomain = MyDomain.ltd;
               SOGoUserSources = (
                   {
                       type = ldap;
                       CNFieldName = cn;
                       IDFieldName = uid;
                       UIDFieldName = uid;
                       MailFieldNames = (mailLocalAddress, mailAlias);
                       baseDN = "ou=MyDomain,dc=MyDomain,dc=ldt";
                       canAuthenticate = YES;
                       displayName = "Addresses MyDomain";
                       hostname = localhost;
                       id = MyDomain.ltd-public;
                       isAddressBook = YES;
                       port = 389;
                    }
            );
            };
            MyDomain2.ltd = {
               SOGoMailDomain = MyDomain2.ltd;
               SOGoUserSources = (
                   {
                       type = ldap;
                       CNFieldName = cn;
                       IDFieldName = uid;
                       UIDFieldName = uid;
                       MailFieldNames = (mailLocalAddress, mailAlias);
                       baseDN = "ou=MyDomain2,dc=MyDomain,dc=ldt";
                       canAuthenticate = YES;
                       displayName = "Addresses MyDomain2";
                       hostname = localhost;
                       id = MyDomain2.ltd-public;
                       isAddressBook = YES;
                       port = 389;
                    }
            );
            };

};

Single domain configuration:
SOGoUserSources = (
{
type = ldap;
CNFieldName = cn;
IDFieldName = uid;
UIDFieldName = uid;
baseDN = "dc=MyDomain,dc=ldt";
bindFields = (uid);
canAuthenticate = YES;
displayName = "Adresses MyDomain";
hostname = localhost;
id = public;
isAddressBook = YES;
port = 389;
scope = SUB;
}
);