Office 365 Migration with Cisco IronPort

I ran across an interesting issue recently where a client could not get Autodiscover to work properly during their “rich coexistence” period with an on-prem Exchange 2010 during their migration to Office 365. Autodiscover for an on-prem user would work fine, but as soon as the user had their mailbox moved to Office 365 the Autodiscover process wouldn’t work. The DNS records looked fine and when looking at the log we saw the client would connect to the internal SCP, get a redirect to Office 365 for the correct SMTP address, and then fail. We couldn’t set up a brand new profile for the user internally, but we noticed it would work perfectly ok from an Internet client. Must be something internal at that point, right?

After some more testing we learned a Cisco IronPort was being used for outbound web proxy filtering. As soon as we added an exception for the test machine’s IP address we found Autodiscover worked just fine for a cloud user. In the end we added an exception for the FQDNs .outlook.com and .online.lync.com. Secure web filtering keeping users safe and admins frustrated. Happy migrating.

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Some personal background, links to related projects, and other ways to connect.

Hi there. My name is Tom Pacyk and this is my small home on the web. I love the intersection of design, technology, and communication, which is a combination that led me to a career in sales and marketing roles at places like Zoom and ServiceNow. They're a bit old now, but I also had the opportunity to publish a couple of books along the way.

Portland, Oregon is home for me, my wife Beth, and our three kids, but I'm actually a Midwestern transplant—I grew up in the Chicago suburbs and went to school at Purdue and Illinois. When I find some free time I'm probably going to concerts, rooting for the Portland Timbers, or working on my Sunshine Burn Photography project.