Some of the reasons why I think it's hard:
* I don't think security was a big deal to many of the mail applications when they were being built. I tried and gave up so many times trying to find a strong hashing algorithm that both dovecot and ruby supported. There was practically no documentation on this and it felt like I was venturing into territory never before seen.
* Parsing emails to be display correctly seems impossible. Sometimes emails have "<br>" in them and sometimes they have "\n". But what if the "\n" doesn't mean newline but it's just what someone wrote in the email? They come in a variety of mime types and formats. It sometimes seems impossible to do this.
* Not everyone uses the RFC standards! I thought the RFC said that a subject can only be 78 chars long. Yet I get emails all day long that go way beyond this which cause major problems in my code. AM I THE ONLY ONE AROUND HERE THAT CARES ABOUT RFCS?