The owner of the e-mail service [Lavabit, Ladar Levison,] said he closed it down after the government, in pursuit of Edward J. Snowden, sought untrammeled access to the protected messages of all his customers. Mr. Levison was willing to allow investigators with a court order to tap Mr. Snowden's e-mail account; he had complied with similar narrowly targeted requests involving other customers about two dozen times. But they wanted more, he said: the passwords, encryption keys and computer code that would essentially allow the government untrammeled access to the protected messages of all his customers. That, he said, was too much. On Aug. 8, Mr. Levison closed Lavabit rather than, in his view, betray his promise of secure e-mail to his customers. On [October 2], a federal judge unsealed documents in the case, allowing the tech entrepreneur to speak candidly for the first time about his experiences. He had been summoned to testify to a grand jury in Virginia; forbidden to discuss his case; held in contempt of court and fined $10,000 for handing over his private encryption keys on paper and not in digital form; and, finally, threatened with arrest for saying too much when he shuttered his business. While Mr. Levison's struggles have been with the F.B.I., hovering in the background is the N.S.A., which has worked secretly for years to undermine or bypass encrypted services like Lavabit so that their electronic message scrambling cannot obstruct the agency's spying. Mr. Levison's case shows how law enforcement officials can use legal tools to pry open messages, no matter how well protected.