Hi there, if you are using Spotify premium account, those are the domains to be whitelisted in order to Spotify function fully on Mac & iPhone apps (including software update):
mobile-ap.spotify.com
apresolve.spotify.com
upgrade.scdn.co
market.spotify.com
spclient-wg.spotify.com
Please also consider adding your findings to:
I'm afraid the topic is closed, no further editing possible.
Hmm, you are right. I re-opened it.
Hi,
I assume the url http://upgrade.scdn.co is supposed to be http://upgrade.scdn.com, correct?
I also noticed on the post here;
spclient.wg.spotify.com is mentioned.
So, is it spclient-wg or spclient.wg?
//AvG
Answering myself after some log studies. 
Using these Spotify whitelistings from the OP, with some edits as well as an addition, to make my mobile phone connect properly to Spotify and my Denon Heos wifi-speakers.
mobile-ap.spotify.com
apresolve.spotify.com
upgrade.scdn.com
market.spotify.com
spclient**.**wg.spotify.com
Refused to connect with the above, unless this one too was whitelisted as well:
audio-ake.spotify.com.edgesuite.net