Asterisk 1.4.26-2 and sip phones : no phonebook lookup


I have a problem with Asterisk 1.4.26-2 and my sip hardphones :
Siemens Gigaset S450IP and Snom M3 (firmware v2.02).

For analog incoming calls (from PSTN), callerid is correctly read by Asterisk,
and displayed by each sip hardphones.

But when the number exits in the phonebook, the phone should display the
contact name instead of the number. But this feature is never working !

Perhaps Asterisk sends the number like “callerid@ip_adress_asterisk” which
could prevent the sip phone to recognize and do the lookup ?
Did I missed something in the configuration files ?

Could you please help me to fix this ?
Thank you.

nb : this feature is working like a charm on my old analog DECT SL560 Gigaset
which is connected to Asterisk via a TDM400P.