ERROR: SMPP[test]: got DLR but could not find message or was not interested in it

I have problem with DLR's through SMPP.

I'm using cvs snapshot, with mysql and dlr.

I use following syntax to send sms:
http://localhost:13013/cgi-bin/sendsms?username=*&password=*&to=*******8&text=Hello+world&dlrmask=31

messages are received on mobile, but I'm getting following error:

ERROR: SMPP[test]: got DLR but could not find message or was not 
interested in it

and in dlr table there is one record per sent message:

 smsc | ts               | destination | service | url  | mask | status |
+------+---------------+-----------------+-----------+-----+--------+----------+
| test | 16776982 | ********         | 1         |         |   31 |     
12       |

Could anyone explain me, what's the problem


Thanks