Gmail turned five earlier this week -- April Fools Day to be exact.

But the original launch was no joke. Gmail, perhaps the longest running app to still be labeled "BETA" shook up the e-mail landscape immediately on its debut and continues to push the envelope with innovative releases.

It's easy to forget that back in 2004 e-mail services like Yahoo Mail and Hotmail were free, but free storage was limited, you had to pay for storage in, for example, 20 to 100 megabyte increments. Google's idea to provide Gmail users with up to a gigabyte of free storage was audacious at the time and compelling enough to force competitors to match it or risk losing users.

Google (NASDAQ: GOOG) also gained by being late to the e-mail party, learning from the mistakes by others. Rather than open up the service to all comers, Gmail started in true beta fashion as a test application that only a limited number of people could access. In the first year, you had to know someone at Google or a Gmail user to be "invited" to sign up. This not only helped control growth, it limited opportunities for spammers and helped the company fine-tune its approach to deal with spam.

[Continue reading this blog post at Eye of the Needle by David Needle]