I knew that Gmail had been around for a long time, but 20 years to the day on 1st April 2004 is quite something. Here's a couple of articles on it.
www.ndtv.com

Gmail Turns 20: All About How The Email Service Was Launched
Gmail anniversary. The service was launched on April 1, 2004, and soon became the undisputed king of email. Twenty yeas later, it boasts of 1.2 billion users.

