The basic concept of Gmail sprouted in the mind of Paul Buchheit back in 1990 but the execution of the concept took around 14 years and the service officially got mounted in 2004. The much easier and user-friendly interface with which the billions of global Gmail users have been blessed today was not the case years back.
The inception of the service was in the beta form and it was nothing more than an essence of freshness in the era ruled by Hotmail
Till 2007, there was a slew of drawbacks and complexities associated with the service and people were already bored with the basic and slow interface of Outlook.com. Firstly Google surprised the users with a huge internal storage that simply outpaced the Hotmail and Yahoo services and then it made the users fall for it by introducing the Cloud storage amenity that left its peers agape.
Gmail always had the futuristic approach to impress its users. A lot of endeavors were put together by the Gmail team to reach this paramount niche and lots of exciting features are still lined up.
Some useful websites for further reading: