Silent Circle also shuttered its encrypted email service a few hours after Lavabit shut down citing an ongoing legal battle.
"We see the writing the wall, and we have decided that it is best for us to shut down Silent Mail now," Silent Circle wrote in a blog post on Friday in reference to the closure by Lavabit.
The company, with U.S. headquarters in Maryland, said it had not received subpoenas, warrants, security letters, or anything else from any government, and "this is why we are acting now."
The closure of Lavabit and Silent Circle reflect concern among email providers about government orders for customer data under the U.S. Foreign Intelligence Surveillance Act. Most of these come in the form of "gag orders" that prohibit the service providers from discussing in public the orders for disclosure of customer data.
Lavabit was reportedly the email service provider for former NSA contractor Edward Snowden, who in June disclosed through newspapers certain documents about surveillance programs by the U.S. National Security Agency.
Owner and founder Ladar Levison said on Thursday that he was shutting down the service rather than become "complicit in crimes against the American people." He said that under laws passed by the U.S. Congress he could not share his experiences over the last six weeks, even though he had twice made the appropriate requests.
Silent Circle will continue to support its Silent Phone encrypted mobile video and voice service, Silent Text, its encrypted business documents service, and its Silent Eyes teleconferencing platform, which it described as end-to-end secure. "We don't have the encrypted data and we don't collect metadata about your conversations," it assured customers.
In contrast, "Email that uses standard Internet protocols cannot have the same security guarantees that real-time communications has," Silent Circle wrote. "There are far too many leaks of information and metadata intrinsically in the email protocols themselves. Email as we know it with SMTP, POP3, and IMAP cannot be secure."
Among Snowden's revelations through media outlets was the charge that Internet companies like Google and Facebook provide real-time access to content on their servers to the NSA, which the companies have denied.
Microsoft and Google have asked a FISA court to allow them to provide aggregate numbers on FISA and related data requests by the government, but the U.S. Department of Justice has postponed replying to the plea four times so far. The FISA court has separately ordered the government to declassify its secret order and parties' briefs in a case which Yahoo expects will demonstrate that it resisted government directives.