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Twenty years ago yesterday, the first e-mail attachment was sent, using a bit of software written by Borenstein called Multipurpose Internet Mail Extensions (MIME).

Our interconnected digital world would not be the same without it.

Appropriately, the attachment Borenstein sent was a picture and a song - a precursor to the "gazillions" of humorous attachments that are e-mailed around the world every day now.

Two decades ago, e-mail was a basic, text-based system - electronic mail in its purest form.

What Borenstein did was add a package service to the electronic postal service - and the ability to share files through the internet came of age. It went from being a postal service (for letters, as it were) to a courier service (for parcels) as well.

Borenstein was also crucially involved in other e-mail initiatives, working on an early program called Andrew when he was at the prestigious Carnegie Mellon University in Pittsburgh in the US.

During this time, he famously turned down a job offer from Steve Jobs - who had recently been fired from Apple and had started his new computer company called NeXT.

"He came to the campus, and a light went off in his mind when he saw the mail system. He had not completely gotten e-mail until he saw what we could do with it," Borenstein said in an interview last week with AllThingsD.

But Borenstein declined Jobs's offer because "I had heard from other people that working for him was difficult ... I had a feeling that if you went to work for him and you had a disagreement with him, you lost. It was that simple."

Borenstein added: "His team built NeXTMail, which looked a lot like Andrew did. In fact, if you use Apple's Mail.app on the Mac, you're using something that looked a lot like Andrew did."

In 1992, while Borenstein was working for a research facility called Bellcore, he realised there was a problem with the compatibility of different e-mail programs and how they encoded their messages, which caused problems with sending files.

He worked with another internet pioneer, Ned Freed, to create MIME, which is now responsible for about one-trillion messages a day. Amusingly, Borenstein was hired as the chief scientist of an e-mail company called Mimecast.

E-mail has become more than a way to send messages. It's evolved into something it was never intended for: It's become some kind of amalgamated to-do list and data repository for user names and passwords, important documents and assorted "must keep" items.

For a cyber criminal, getting access to someone's e-mail means they have a handy way to steal that person's identity.

Additionally, and sadly, your e-mail address is usually the recovery mechanism for forgotten passwords. Always use a secure password, with capitals, numbers and other symbols - never just a word from a dictionary.

E-mail has expanded our inbox experience in so many more ways now; and it would never have been what it is without Borenstein's work part of which, he jokingly said at the time, was to be able to receive photographs of his grandchildren one day.

• Shapshak is editor of Stuff magazine