Solution : https://service.sap.com/sap/support/notes/604495 (SAP Service marketplace login required)
Key words :
temsgu-bdate = sy-datum, last_usr_emsg = temsgu-bid, bname = sy-uname, mndt = sy-mandt, langu = sy-langu, function group sm02, function module sm02_get_unread_message, system messages reason, sy-subrc = 0, system messages
Related Notes :
| 808288 | SRM: System messages are not displayed on the browser. |
| 302696 | SM02 system messages, changes for Release 6.x |