Exchange can be just the tip of the iceberg. Our organization had a hundred or so custom applications and databases in Notes. That being said, Exchange migrat

Exchange can be just the tip of the iceberg. Our organization had a hundred or so custom applications and databases in Notes. That being said, Exchange migration can be really tricky too depending on your retention policies, legal obligations around data preservation, and other factors. If you're doing onprem installs of Exchange rather than hosted solutions, you also have to worry about disaster recovery. Say what you want about LN but it's built-in backup, retention, and recovery mechanisms put Exchange and even most Databases to shame. I wasn't directly involved in our org's migration but from what I understand, the org waited until it had settled most or all outstanding litigation before attempting to migration. When they did, we changed our data retention policy for email from forever to 6 months before starting. This significantly reduced the volume and scope of work. And I think we kept the 6 month policy after migration because it's legally advantageous.