Play sound with xmailbox

[Guido Bozzetto <GB@Nauta.it>]

I'm trying to use the sound playing without success.
How I can play a sound when arrive e new message ?
I've tried with:

.Xresources:
*xmailbox*mailsndfile:  /usr/doc/xmailbox/examples/dingdong.au
*xmailbox*mailsndcomm:  /usr/bin/play %s

but I'm hearing only the internal speaker bip.

                                     Thanks Guido.
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