[OpenSER-Users] Forward to voicemail when not registered

I want to provide for forwarding of calls to voicemail in various circumstances, one of which is when the user is not registered with the registrar. I've looked at various example configuration files that include forwarding (e.g. http://www.sipwise.com/wizard, onsip.org) and have not seen an implementation of this. Could anyone provide any tips regarding this or is it as simple as: route[3] { # ----------------------------------------------------------------- # INVITE Message Handler # ----------------------------------------------------------------- <snip> if (!lookup("location")) { if (avp_db_load("$ruri/username", "$avp(i:20116)")) { avp_pushto("$ruri", "$avp(i:20116)"); t_relay; return; } else { sl_send_reply("404", "User Not Found"); return; }; <snip> Am I missing something obvious or is this really quite simple? Regards Cameron