Res_external_mwi module

Hello,
I have a few Asterisks linked together via a VPN, but only one of them is used for voicemail. I would like devices registered on the other Asterisks to show MWI when there is voicemail. res_external_mwi module seems to be the answer, but I cannot find any documentation on how to use it. Can anyone give an example?

Thanks,
Ian.

That module is not for directly exchanging MWI between systems. It is used by ARI to allow application developers to control MWI. You could certainly write your own solution if you wanted using that.

Thanks for clarifying Do you have any other suggestions for how to do it?