There are 2 sip applications installed in my series60 2.1 emulator: Chipflip and SIPExample. To my understanding, in order to make the SIPExample that can receive the INVITE message, I have to modify the SipAppCapabilities.xml under directory C:\Symbian\7.0s\Series60_v21_B\Epoc32\wins\c.
The original SipAppCapabilities.xml which is created by chipflip example:
And then I run the sipclientinstaller.exe under directory C:\Symbian\7.0s\Series60_v21\Epoc32\release\wins\udeb to let the emulator know the update. However, when I start the SIPExample and try to invite another player, there is a dialog pop up which shows: