GPs in England must start routinely using email instead of sending letters to communicate with patients, the health secretary says.
Matt Hancock wants email to become the default option by 2021.
He said there was no reason why doctors could not email a test result or prescription – although people who did not use email would still be able to request letters were sent.
It comes after he ordered fax machines to be phased out by next year.
Research shows there are still more than 8,000 fax machines being used by the NHS.
Mr Hancock said: “Having to deal with outdated technology is hugely frustrating for staff and patients alike – and in many cases downright dangerous.
“A letter lost in the post could be the difference between life and death.
“There is no reason why a doctor cannot email a patient confidentially, for example with their test results or prescription, rather than make them wait days for a letter or ask them to come in to the surgery.
“The rest of the world runs on email – and the NHS should too.”
He said that NHS organisations could use any secure email provider – not just NHSMail – if it met the required security settings, in a bid to support innovation and open up the market.
Dr Helen Stokes-Lampard, who chairs Royal College of GPs, said: “Aspirations to use less paper and more modern communication techniques to improve the way we work with colleagues and improve patients’ experience of the health service are good.
“But the practicalities of how we do it need to be thought through carefully – current IT systems in the NHS are often clunky and frustrating.
“But there isn’t an easy fix and it is difficult to see how the wholesale changes being advocated can be done safely in the timescales being spoken about.”