Last month, secure email service Lavabit, which had been used by NSA whistleblower Edward Snowden, shut down following a government surveillance order.

"I have been forced to make a difficult decision: to become complicit in crimes against the American people or walk away from nearly ten years of hard work by shutting down Lavabit," said the firm's founder Ladar Levison.

Just hours after Levison's announcement, encrypted communications specialist Silent Circle announced that it "can see the writing on the wall" and abruptly followed suit, without forewarning.

Speaking at a roundtable event on Thursday, Silent Circle CEO Mike Janke explained the decision in more detail following questions from ITProPortal.

"We knew customers would be upset, we knew we would lose a lot of money, but it came to the point where it wasn't about money," he said.

"We don't have contacts for clients so the only way of letting them know would have been to put a blog post out saying that we are shutting the service down in 12 hours. That would have been an advert to all the world's law enforcement, giving them 12 hours to subpoena us, so we decided to just shut it down."

No government would have been able to access the content of the emails, but what would have been available is the metadata - who contacted who, the time, place and subject line - which can never be hidden through email, Janke explained.

"Email is fundamentally broken, the architecture of email was made 40 years ago," he said, adding that email also has keys held on a server that can be accessed. "We could have been coerced by a number of governments to hand over the metadata and all that metadata is just as valuable as the content."

"We were holding a veritable golden goose of information including that of the Dalai Lama and others including special operation units. We knew was only a matter of time before someone came to us," Janke explained.

This is not the end of Silent Circle's foray into encrypted email however. Janke also revealed that the previous system had always been a temporary fix, whilst the company developed a secure email app that runs on Silent Circle's peer to peer encryption used by Silent Phone and Text, it's just taking longer to develop than first hoped.

"We thought we'd have it done sooner, so the encrypted email was a stopgap, but we became a lot more popular around the world than expected, and suddenly we had a lot of data. So when we saw the subpoena against Lavabit, because of Snowdon, we scorched earth, we had to," he said.