As usage evolves, the Internet technology remains remarkably stable. The mail system I was using 10 years ago on a Digital VAX still works with today's email. Don't break something that works is the rule among the Internet architects. This is remarkable because IT is now largely dominated by rapid obsolescence and poor backward-compatibility. For example, you can't open a Word 97 document with Word 95.
Internet technologies are more resilient by nature.
By now you may wonder where I'm heading. Bear with me, I'm getting there. I'm heading towards modularity. The Internet has proved so resilient to change because the architecture is highly modular. One can combine these building blocks, or create new blocks, as needed to improve Internet email.