The massive inconveniences others have pointed aside, it will be a technical nightmare to implement too. Incoming email takes a _lot_ of moving parts to process

The massive inconveniences others have pointed aside, it will be a technical nightmare to implement too. Incoming email takes a _lot_ of moving parts to process. What could have been a simple http get/post/redirect forms now need a process to accept and parse incoming emails, and someone inform the page about verification status. There are plenty of existing libraries and software to do it, but it's really difficult to get right. Incoming emails in qprint, plain and html emails with boundaries, spoofed emails, separating verification emails from regular emails, etc there are so many complexities involved. In addition, it is difficult to write unit tests for them, and integration tests wouldn't be solid either. All of these technical complexities to beat a paradigm that billions of users are used to, with no obvious improvement.