Spotify desktop client just stopped working on corporate network company wide

[kpwern]

When I investigated the firewall, I saw port 4070 being dropped outbound.  To test I opened up that port and Spotify began working again.  We've never had 4070 allowed outbound and I was under the impression that the desktop client is designed to attempt 4070 and failover to 443 if a connection is unable to be established.  Is this a common issue?