die if no sendmail executable is available

lib/IdPAccountManager/Tools.pm

@@ -113,6 +113,9 @@ sub update_ssp_authsources {
 sub mail_notice {
     my (%args) = @_;
 
+    die "unable to send mail, no sendmail executable found"
+        unless -x '/usr/sbin/sendmail';
+
     open SENDMAIL,
         "|/usr/sbin/sendmail -f $args{data}->{from} $args{data}->{to}";