Sophos proxy stops Internal Outlook clients from accessing AutoReplies/MailTips/Shared Calendars

Question

Dear Sophos Community, 
 We have the above issue, the proxy is pushed out to clients via GPO and within that we specify what can be accessed (which for us should be local addresses) 
 
 If it take a machine out of the proxy scope, everything works brilliantly. Is there something I'm missing with regards to allowing internal clients to access autodiscover, etc.. 
 
 Thanks in advance..

RegencyBlue · Answer

Hi Bob, 
 
 Thank you for replying :) 
 I'm not even kidding in the last hour I've managed to sort this out. 
 
 Turned out the advanced exclude proxy list in Internet settings was configured wrongly. I made sure that as well as getting the internet IP's I wanted it to skip I also made sure I listed msstd*.contoso.com at the very bottom, which is the only place it seems to work. 
 
 Then after a gpupdate /force on a user logged into that OU. Log back in and do chrome://net-internals/proxy it should show you what is applied. 
 
 Needless to say everything is now working how it should be.

DouglasFoster · Answer

The URL is interpreted as text, so you need to exclude the internal URLs by name as well as by IP address, on the assumption that they will be referenced both ways. 
 I have tried to use this forum to document everything that I figured out as I worked with web filtering, because the manuals do not provide any tutorials. My earliest material is in the WiKi section, and generally foundational. The newer material is (courtesy of the moderator) pinned at the top of the Web Filtering sub-forum. The most recent entry is "Troubleshooting Web Filtering", which I hope you may find useful for rapid response to the next problem. "Web Filtering Lessons Learned" is the longest document. It includes a sample proxy script, an explanation of why I use both Standard Mode and Transparent Mode together, and related matters. 
 In the Wiki, there is a post about the UTM Architecture, which contains undocumented information that I learned by unhappy surprise, a tutorial about how the different pieces of the web filtering configuration work together, and a discussion about the different security mechanisms and how they fit together.