One new email service promising "end-to-end" encryption launched on Friday, and others are being developed while major services such as Google Gmail and Yahoo Mail have stepped up security measures.
A major catalyst for email encryption were revelations about widespread online surveillance in documents leaked by Edward Snowden, the former National Security Agency contractor.
"A lot of people were upset with those revelations, and that coalesced into this effort," said Jason Stockman, a co-developer of ProtonMail, a new encrypted email service which launched on Friday with collaboration of scientists from Harvard, the Massachusetts Institute of Technology and the European research lab CERN.
Encryption is a tool that can help dissident activists avoid detection in places like China or Iran, but the movement has also gained credence in the United States among those who want to stay clear of snooping from the NSA or other intelligence services.
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"Our vision is to make encryption and privacy mainstream by making it easy to use," Stockman told AFP. "There's no installation. Everything happens behind the scenes automatically."
After testing over the past few months, ProtonMail went public Friday using a "freemium" model -- a basic account will be free with some added features for a paid account.
"As our users from China, Iran, Russia, and other countries around the world have shown us in the past months, ProtonMail is an important tool for freedom of speech and we are happy to finally be able to provide this to the whole world," the company said in a blog post.