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WebFilter and https://outlook.office.com or https://outlook.office365.com "Host not found" HELP

Okay, so I have setup the Web Filtering and using the transparent mode. I have added exceptions for Office 365 as we're using Microsoft Office 365 for SharePoint and Exchange. Which all has been working well and I cannot tell by the error what is occurring here when the Outlook Web Access (OWA) is reporting invalid HTTPS cert (from the UTM) as well the error reads Host not found.

UTM Error Page:

While trying to retrieve the URL:
The content could not be delivered due to the following condition:
Host not found
Your cache administrator is:
MyEmail@apexanalog.com
Testing done:
I have reviewed  the web filter live log (if you would like to see) which shows status codes 200, 502 then final of 304.
The Base Policy is one that states blocks when testing https://outlook.office.com/owa the exception is listed. The Reason is Host not found. So, I am really lost with this error reason. https://outlook.office365.com/owa works with the Policy HelpDesk. Is this a DNS issue cause testing this in browser it varies from outlook.office.com to outlook.office365.com.
I cannot figure out where this is getting hung up. I have web filter options to allow many Office 365 items. This is the only one complaining. The SSL warning before reaching the page is from Astaro the UTM, and I did not think I would get such since I am using transparent mode web filtering.
Please let me know what I can look at, at this point I am drawing a blank. There is no reason I see as to why this should be occurring.
Any assistance would be greatly appreciated. Thanks in advance!


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Parents
  • One of my client resolved Office 365 problems with this exception. Also try with Bob's suggestion including AV and SSL scanning in exception object.

  • Guys,
    Sorry for the delay. This is now working. This particular instance was a bad Host record that I was using. The old IP address, hence the UTM not being able to reach. It occurred when initially setting up and had forgotten about, needing to go back and change. Removing this static host record corrected the situation.

    Thank you Vilic, I have similar setup and find its key to Office365 DNS. These are setup in Filtering Options/Exceptions.
    Bob, thank you as well. I will keep this option in mind if needed in future.
  • We are experiencing this issue. The certificate error is for "companyname.onmicrosoft.com"

    I have tried importing the certificate, but the error persists.

    I tried the exception list above, and also added onmicrosoft.com to the list. This doesn't work either.

    The only solution I have found is to add "onmicrosoft.com" to the proxy exception list on the client. This is awkward for 200+ users and requires us to keep masquerading open.

    I am really hoping for a better solution. Any ideas?

    Thanks,

    Alan

  • Alan, have you tried using a GPO to get that Exception out to all of the clients?  Are you in Standard or Transparent mode?  How does your setup compare to DNS best practice and Configuring HTTP/S proxy access with AD SSO?

    Cheers - Bob

     
    Sophos UTM Community Moderator
    Sophos Certified Architect - UTM
    Sophos Certified Engineer - XG
    Gold Solution Partner since 2005
    MediaSoft, Inc. USA
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