Lock Account with OL2000

[David]

I use exchange 2000 (Sp3) + OL2000 (SP3)
I found that my OL network secuity is changed to "None"
It will pop up a window for logon if I open OL

But if enter wrong message, my Account will be locked.

I have check my Domain Group Policy.
The account will be locked only if logon over 5 times


Any one can help me??
THX