You forgot 3- a search function that worked well and instantaneously. and you kind of covered it, but just to make it explicit- provided what was practically

You forgot 3- a search function that worked well and instantaneously. and you kind of covered it, but just to make it explicit- provided what was practically unlimited storage for the time- 2GB. Competitors were offering 5, maybe 10MB. I remember people hacking together a file system out of it because that was so astoundingly large for the time. The fact that gmail is now taken for granted is quite interesting though, it really was astoundingly revolutionary at the time and really built the halo image around Google.