Issues with firewall settings

[hniehus]

Hi,

I have some strange behavior of my zentyal firewall (zentyal 3.5.3) that I can't get worked out. Here is what happens:
My network is composed of a gateway (192.168.2.1), the zentyal server (192.168.2.2) and three client devices
- laptop (192.168.2.100)
- Android (192.168.2.105)
- Android (192.168.2.113)
So ALL devices are within the same address range. Ok, good.
I can access my IMAPS service (port 143) and the HTTPS service (port 443) with my laptop, but with neither of the android although they are in the same address range.
Whenever I'm flushing my iptables and rebuild the zentyal rules I can connect my Androids through WLAN exactly once. After that one connection every following connection will be refused.
I see a lot of packet-filter DROP messages in the kern.log even for packets from/to the androids, while packets from the laptop walk through easily.
However, when I'm disabling WLAN on my Androids, connecting to IMAPS or HTTPS through mobile networking (having an external IP) works fine.

I'm not able to get on top of what the issue is with my firewall settings. Any help would be appreciated.

Thanks,
Harald

[hniehus]

Anyone?
Digging into my kern.log I found a lot of stuff like

zentyal-firewall drop IN=eth0 OUT= MAC=00:13:d4:b7:2b:28:00:73:e0:8f:5c:37:08:00 SRC=192.168.2.114 DST=192.168.2.2 LEN=52 TOS=0x00 PREC=0x00 TTL=64 ID=22537 DF PROTO=TCP SPT=56414 DPT=443 WINDOW=319 RES=0x00 ACK RST URGP=0

where 192.168.2.114 is now the IP of my android. So iptables seems to drop reset request for already acknowledged packets.

Any idea, why is that?

Thanks,
Harald