HTML TOP header is not shown in mail

Hi

I've an ALV for sending a list thru mail correctly, but when user open it HTML top header is not shown

FM

CALL FUNCTION 'REUSE_ALV_GRID_DISPLAY'
    EXPORTING
      i_callback_program          = sy-repid
      i_callback_html_top_of_page = 'HTML_TOP_OF_PAGE'
      i_structure_name            = 'ZMMALV_01'
      it_sort                     = gt_sortinfo
    TABLES
      t_outtab                    = it_data01.

FORM html_top_of_page

text = 'Time : '.
  CALL METHOD top->add_text
    EXPORTING
      text         = text
      sap_emphasis = 'Strong'.

  CALL METHOD top->add_gap
    EXPORTING
      width = 6.

  text = sy-uzeit.
  CALL METHOD top->add_text
    EXPORTING
      text      = text
      sap_style = 'Key'.

  CALL METHOD top->new_line.

Thanks in advance.