I wouldn't use feature-completeness as the goal. I was a Gmail user since it was released[0], and while it was certainly unique back then, I realized recently

I wouldn't use feature-completeness as the goal. I was a Gmail user since it was released[0], and while it was certainly unique back then, I realized recently that almost none of the features I use nowadays are Google-specific[1]. In fact, the one major annoyance of Google's mail services for me is IMAP! Namely - Google provides an IMAP-like interface, but it isn't quite the same as IMAP, and it has a number of warts that make it not impossible to use, but certainly uncomfortable. I have seen a number of mail/IMAP clients literally special-case Google's idiosyncrasies into their IMAP handling because of this. [0] Now it's 2014, and it feels kind of weird to think that I've had my Gmail account for almost 10 years. [1] Even in 2004, most of what Gmail provided was unique to web-based email, but had been around for a while on desktop mail clients. That, and the 1GB of storage, which felt excessive at the time (how things change!).