[Asterisk-Users] Mulitple voicemail on mulitple phones

[kurt x]

I have four DIDs.  2400,2401,2402, and 2403

There is no phone attached to 2400 but the other three DIDs do have
phones attached

All the four DIDs have their own voicemail and voicemail works on all
the DIDs.  When you dial 2400 it rings the other three numbers.  If no
one picks up, it goes to the 2400 voicemail box.  What I need to
understand is how to notify the other three phones that voicemail was
left on the 2400 extension.
The other three DIDs must be able to access the 2400 voicemail, and delete it.

Any ideas.

Kurt