On a very quick view i saw many diffrent other ports then 80 or 443 thats why i start to blind guessing 
For example here but i read it not carefully maybe its something total diffrent what he talk
I know iDomiX and his videos but his setup seems to be different from mine.
I assume he uses a much more simpler setup with only a port forwarding from a modem like the Fritzbox with integrated firewall and not like in my case a dedicated firewall behind the Fritzbox.
Your setup is for sure diffrent but the port must be the same on your Syno As i said iam sure we find a solution Sooner or later… 
1 Like
… but not today I now will have a break and go to bed.
Thanks so far,
Michael
Very good idea
NP, i really love to help no matter in what way
Another good link
What network ports are used by Synology services
Synology CardDAV Server 8008 (HTTP), 8443 (HTTPS) TCP
Good morning!
This ports are standard ports of Synology’s own CardDAV server, to be precisely: this CardDAV server installs its own web server and adds two new ports as mentioned in your posting above.
I’m running Baikal CardDAV server which is an adopted Radicale server. This service or better its PHP files are installed directly on the native web server of the NAS, hence no new ports necessary, just 80 and in my case 443.
Thanks for all comments and help so far,
Michael
A possible weired idea:
What if I set up a VPN connection on the Fritzbox that will connect to IPFire if the IP-addressoor network 192.168.6.96 gets addressed?
See wiki https://wiki.ipfire.org/configuration/services/ipsec/avm-fritzbox
Don’t know if the Fritzbox can open the connection itself or if only clients attached to the box can do so.
Nevertheless you should forward to the right network.
192.168.6.96 is not part of 192.168.0.0/24.
So in other words i can stop searching a Syno solution because you use a Third Party thing
So what are the next steps? Lets start with /16 Subnet Mask Do a Port Forwarding Rule, Source Fritzbox to Syno green Port 443.
The VPN is the absolute best solution because you love offering services in green But we need here a VPN expert or you RTFM (AVM)
@hellfire you could have avoid all these problems with a real modem in front of your ipfire.
ipfire as an exposed host may be “OK” in some scenario, but it is for sure not a real good solution !
greetings Robert
Hi Robert,
I had this setup before but had to exchange the “dumb” provider cable modem (in bridge mode) with the Fritzbox because I wanted to use my cable providers SIP telephonie features (assign a deidicated phone number to certain devices) and had to register some DECT phones with the Fritzbox as the DECT basis.
There is even a longer story about consolidating some hardware and phone features but that’s too much for this thread .
With your own cable modem (not provider device in bridge mode) Vodafone also has to provide SIP Data.
For example I use a TC4400 + Firewall + APs + 7490
Gruß Robert