Sorry for the late response, put these lines inside /etc/e-smith/templates-custom/etc/ejabberd/ejabberd.cfg/80Ports20s2S
{
$OUT .= "\n";
$OUT .= ' ,{5269, ejabberd_s2s_in, [{shaper, s2s_shaper}, {max_stanza_size, 131072}]}';
$OUT .= "\n";
}
Then execute:
signal-event nethserver-ejabberd-update
I tested it on a dev machine.