Hi,
ok, set mtu on upstream gw to 1400, and everything remains as before :-( (didn't check at the upstream gw yet, but from inside the mesh i can also access hotmail when 1-way-tunnel, and not access hotmail when 2-way-tunnel) and tried another one with mtu 1200... still the same, seems not related.
one more idea: Do you clamp the MSS on the batman gateway client ? It is somehow related to the MTU problem. You can try this iptables command: iptables -I FORWARD -p tcp --tcp-flags SYN,RST SYN -j TCPMSS --clamp-mss-to-pmtu
Regards, Marek