Silent Circle has also discontinued its mail encryption service.
Email service Lavabit has suspended operations over concerns that the US government could spy on users of the service.
It had been reported that whistleblower Edward Snowden had been using the email service while he was based in Moscow Airport.
In a statement to customers, Lavabit owner Ladar Levison said that he had been forced to make a difficult decision – become complicit in crimes against the American people or walk away from nearly ten years of hard work by shutting the email service down.
"After significant soul searching, I have decided to suspend operations," he said. "I wish that I could legally share with you the events that led to my decision. I cannot. I feel you deserve to know what’s going on–the first amendment is supposed to guarantee me the freedom to speak out in situations like this.
"Unfortunately, Congress has passed laws that say otherwise. As things currently stand, I cannot share my experiences over the last six weeks, even though I have twice made the appropriate requests."
Levison has already started preparing the paperwork needed to continue in what he described as the fight for the Constitution in the Fourth Circuit Court of Appeals.
"A favourable decision would allow me resurrect Lavabit as an American company," he added. "This experience has taught me one very important lesson – without congressional action or a strong judicial precedent, I would strongly recommend against anyone trusting their private data to a company with physical ties to the United States."
Following the suspension of the service, encryption provider Silent Circle has also taken action, discontinuing its Silent Mail service in order to prevent spying.
The security firm explained that it has originally designed its phone, video, and text services (Silent Phone, Text and Eyes) to be completely end-to-end secure with all cryptography done on the clients and our exposure to your data to be nil.
"Silent Mail has thus always been something of a quandary for us," the company explained in a post on its website. "Email that uses standard Internet protocols cannot have the same security guarantees that real-time communications has. 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.
"And yet, many people wanted it. Silent Mail has similar security guarantees to other secure email systems, and with full disclosure, we thought it would be valuable.
"However, we have reconsidered this position. We’ve been thinking about this for some time, whether it was a good idea at all."
After hearing that Lavabit had been suspended, Silent Circle said it saw "the writing on the wall."
"We have decided that it is best for us to shut down Silent Mail," the company’s statement added. "We have not received subpoenas, warrants, security letters, or anything else by any government, and this is why we are acting now.
"We’ve been debating this for weeks, and had changes planned starting next Monday. We’d considered phasing the service out, continuing service for existing customers, and a variety of other things up until today. It is always better to be safe than sorry, and with your safety we decided that in this case the worst decision is no decision.
"We are still working on innovative ways to improve secure communications. Silent Mail was a good idea at the time, and that time has passed."