Meeting Request appearing in calendar

Our company is using MS Exchange 5.5 and client is MS outlook 2000.

The situation is that when A send a meeting request to B in a definite time
schedule. B does nothing once he receives the meeting request. Will this
meeting request appear in the calendar in the scheduled time? Most of our
secretaries said that it will appear in B?? calendar (in light blue colour
mark) automatically even he does not open the meeting request mail. They
said
it worked before but not recently.

After we tested, the receiver should require opening the meeting request
mail and the appointment will then appear in calendar (even without
answering
by accept or decline).

Does anyone get the idea of that? Can anyone simulate the similar suitation?
will the appointment only appear when someone open the meeting request mails
or do nothing at all?

Many thanks,

DDT