Erro ao chamar o email padrão

procedure TfrmPesquisaGrupoEmail.prEnviarGrupoEmailStatus;
var qryClienteAux:TQuery;
    vemail:pchar;
    sClientes   :String;
    iRegistros;
begin

    qryClienteAux:= TQuery.create(self);
    qryClienteAux.DatabaseName:= FPrincipal.DatabaseSistema.DatabaseName;
    qryClienteAux.Sql.Text:=´Select Cod_Cli,Imprimir,Nome_Cli,email_cli From CadCliComercio Where (email_cli is not null and email_cli<>"") and (Status_Cli = :ParStatus) Order By Nome_Cli´;
    qryClienteAux.ParamByName(´ParStatus´).AsString := VartoStr(DBLookupComboBStatus.KeyValue);
    qryClienteAux.Open;
    iRegistros:=qryClienteAux.RecordCount;
    qryClienteAux.first;
    While not qryClienteAux.Eof do
    begin
        if iRegistros>1 then
          sClientes:=sClientes+(qryClienteAux.fieldByName(´Email_Cli´).AsString+´;´)
        else
          sClientes:=sClientes+(qryClienteAux.fieldByName(´Email_Cli´).AsString);
       iRegistros:=iRegistros-1;
       qryClienteAux.Next;
    end;
    qryClienteAux.first;

    vemail:=pchar(´mailto:´+sClientes+´?´);
    ShellExecute(Handle,´Open´,vemail,nil,nil,sw_shownormal);
    qryClienteAux.Close;
end;