Email is wonderful and terrible. SMTP is pretty simple, and everyone with a static IP can run their own email server. Configuring it requires some study, but

Email is wonderful and terrible. SMTP is pretty simple, and everyone with a static IP can run their own email server. Configuring it requires some study, but it's not too hard. OTOH creating email clients is hard. I wrote a web server and wanted a webmail client. Basic SMPT messaging is straightforward enough, but MIME is a confusing tangle of protocols and rules that is difficult to understand and implement correctly. I mostly succeeded but it took a long time. Part of the problem is the complexity means protocols are often violated and my webmail client has to deal with loads of exceptions to protocol rules to work in the real world. But that's hardly limited to email. Look at http, it has arcane rules too, and some of the common security issues on the net are the result of "sloppily" implementing programs using http. (You know, XSS attacks, SQL injections and so on.) Email has warts but what doesn't. Certainly email "replacements" will have warts too, especially as they are extended to cover the breadth that email has encompassed.