Index: apps/app_voicemail.c
===================================================================
--- apps/app_voicemail.c	(revision 37143)
+++ apps/app_voicemail.c	(working copy)
@@ -5949,6 +5949,7 @@
 		AST_APP_ARG(mbox);
 		AST_APP_ARG(options);
 	);
+	static int dep_warning = 0;
 
 	if (ast_strlen_zero(data)) {
 		ast_log(LOG_ERROR, "MailboxExists requires an argument: (vmbox[@context][|options])\n");
@@ -5957,6 +5958,11 @@
 
 	LOCAL_USER_ADD(u);
 
+	if (!dep_warning) {
+		dep_warning = 1;
+		ast_log(LOG_WARNING, "MailboxExists is deprecated.  Please use ${MAILBOX_EXISTS(%s)} instead.\n", (char *)data);
+	}
+
 	box = ast_strdupa(data);
 
 	AST_STANDARD_APP_ARGS(args, box);
@@ -5982,6 +5988,30 @@
 	return 0;
 }
 
+int acf_mailbox_exists(struct ast_channel *chan, char *cmd, char *args, char *buf, size_t len)
+{
+	struct ast_vm_user svm;
+	AST_DECLARE_APP_ARGS(arg,
+		AST_APP_ARG(mbox);
+		AST_APP_ARG(context);
+	);
+
+	AST_NONSTANDARD_APP_ARGS(arg, args, '@');
+
+	ast_copy_string(buf, find_user(&svm, ast_strlen_zero(arg.context) ? "default" : arg.context, arg.mbox) ? "1" : "0", len);
+	return 0;
+}
+
+static struct ast_custom_function mailbox_exists_acf = {
+	.name = "MAILBOX_EXISTS",
+	.synopsis = "Tell if a mailbox is configured",
+	.desc =
+"Returns a boolean of whether the corresponding mailbox exists.  If context\n"
+"is not specified, defaults to the \"default\" context.\n",
+	.syntax = "MAILBOX_EXISTS(<vmbox>[@<context>])",
+	.read = acf_mailbox_exists,
+};
+
 static int vmauthenticate(struct ast_channel *chan, void *data)
 {
 	struct localuser *u;
@@ -6610,6 +6640,8 @@
 	res |= ast_unregister_application(app4);
 	res |= ast_cli_unregister(&show_voicemail_users_cli);
 	res |= ast_cli_unregister(&show_voicemail_zones_cli);
+	res |= ast_custom_function_unregister(&mailbox_exists_acf);
+	
 	ast_uninstall_vm_functions();
 	
 	STANDARD_HANGUP_LOCALUSERS;
@@ -6624,6 +6656,7 @@
 	res |= ast_register_application(app2, vm_execmain, synopsis_vmain, descrip_vmain);
 	res |= ast_register_application(app3, vm_box_exists, synopsis_vm_box_exists, descrip_vm_box_exists);
 	res |= ast_register_application(app4, vmauthenticate, synopsis_vmauthenticate, descrip_vmauthenticate);
+	res |= ast_custom_function_register(&mailbox_exists_acf);
 	if (res)
 		return(res);