Office 365 click-to-run updates not downloading when users inside corporate network

Hi all

We're currently rolling out Office 365 pro plus (click to run) and using the following settings in the configuration.xml file:

<Configuration>

  <Add SourcePath="" OfficeClientEdition="32" >
    <Product ID="O365ProPlusRetail">
      <Language ID="en-us" />
    </Product>
  </Add>  -->

  <Updates Enabled="TRUE" />

I have been informed that <Updates Enabled="TRUE" /> sets the client to download updates from the internet, and generally this works if a client is connected directly to the internet via home broadband etc.

The problem we are seeing is that when users are in the office, updates do not tend to work at all / or very reliably.  And if you manually initiate an update, the update dialogue gets stuck on "downloading updates".

My question is; how does the update process work?  Do i need to add some URL exceptions to our corporate proxy server and/or firewall to ensure these updates work reliably when users are in the office?

Is the update process port 80 or 443 traffic?

Thanks for any help and advice