External Sharing in SharePoint and OneDrive is changing: What You Need to Know

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In an ongoing effort to create a more secure environment by default, Microsoft is introducing an important security update that will affect how external users access content shared through SharePoint and OneDrive. Starting July 1, 2025, any links shared with external users before your organization enabled Microsoft Entra B2B integration will no longer work. This change applies to all organizations that have already enabled or will enable SharePoint and OneDrive integration with Microsoft Entra B2B (Most organizations I have looked into so far). External users trying to use old links will see an error message saying the organization has updated its guest access settings. To regain access, the content must be reshared. Highlights of how the change affects organizations who have enabled B2B: All external sharing will require guest registration. External users must be added as guests in your Microsoft Entra directory. Access will be managed through Microsoft Entra B2B Invitation Manager. T...

502_3 bad gateway IIS AAR RP for Lync

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I encountered a "new" error message this week, as I was finalizing a Lync 2013 deployment for a customer. When I say new, it was new to me, as I had not seen this before. Everything was set up for remote access and federations, but certain features, such as mobility did not work right away. I decided to test the URL's from the outside, and was surprised to find the following error message:


This deployment was set up with a IIS ARR for reverse proxy. I searched for the 502 (502.3 to be exact) on forums and internet in general, but could not find any answer to my exact issue.

I verified firewall ports and connectivity was ok. I also checked the web sites on port 4443 and 8080 from a client inside, and saw no apparent errors.

I went through the deployment guide one more time (step by step), and discovered I had forgotten to import the internal CA ROOT to the Reverse Proxy machine. Once this was installed, it all worked just fine.

The reason I decided to write this post, is because the root cause was not very obvious to me (only after reading tracing logs and checking the step by step guide again, was I able to figure out the problem). And I wanted to write a reminder to myself, and maybe help somebody else if they happened to forget to import the ROOT CA.

The 502 "invalid response" can be a lot of things. Certificate error being one of them. Now I know.

For those looking for a guide to set this up, I have two links for you:
This is the one I used: http://uclobby.wordpress.com/2013/08/02/configuring-arr-for-lync-server/

And here is one from nexthop: http://blogs.technet.com/b/nexthop/archive/2013/02/19/using-iis-arr-as-a-reverse-proxy-for-lync-server-2013.aspx

I preferred the first one, as it was a more "general" rule to catch all. But it might not suit all scenarios. The one from nexthop is much more detailed, and will have you set up a rule for each URL.