So I'm pulling my hair out over this one, when we try to connect to an external non-federated Skype meeting it fails, we have enabled public connectivity in the skype config, we have no problem connecting to federated partners and non federated people can connect in to us.
When i click on the meeting invite in outlook it opens the Skype client
I then get in about 2 seconds an error "An error occurred during the Skype meeting"
looking at the snooper logs for the client and the edge and fruntend I can see


now from my edge i can resolve the SRV records of the domain I'm trying to connect to, I can telnet to them on port 5061 and 443 from the edge, I can resolve SIP.domain.com, AV.domain.com and WEB.domain.com, the network team says there is no blocks showing in or out to any of the domain.com's IP's.
The firewall guys have also seen that my skype client is trying to go directly (via the internet gateway)to the sip.domain.com address on port 5061 and being Blocked ? I didn't think the client should try to go out directly on port 5061 when I'm on the local LAN?
looking at some network capture from my client machine I am seeing some successful traffic going out on 443 which i guess is my client reaching out the other sides proxy?
I'm seeing some stuff online that says the client will always go via the frontend then Edge when connecting to external non-federated web conferences and I found some stuff that says no, the client will try to go directly to the invite originator.
Now i have done days of googling but what I would like as much as an answer/fix is a definitive view on the data flow when a skype client on a company lan tries to connect to an external meeting at a non-federated company, what is involved?
hope this makes sense and thanks in advance for any help anyone can provide.