Just came across this info on Washington’s Blog. Although I was warned long ago to have no expectation of privacy for anything sent over the Internet, for those who had greater expectations, according to Wikipedia:
After 180 days in the U.S., email messages lose their status as a protected communication under the Electronic Communications Privacy Act, and become just another database record. After this time has passed, a government agency needs only a subpoena—instead of a warrant—in order to access email from a provider. Other countries may even lack this basic protection, and Google’s databases are distributed all over the world.
Email sent by employees through their employer’s equipment has no expectation of privacy; the employer may monitor all communications through their equipment. According to a 2005 survey by the American Management Association, about 55% of US employers monitor and read their employees’ email. Even attorney–client privilege is not guaranteed through an employer’s email system; US Courts have rendered contradictory verdicts on this issue.
And from a 2013 ACLU article:
New documents released to the ACLU under the Freedom of Information Act reveal that the IRS Criminal Tax Division has long taken the position that the IRS can read your emails without a warrant—a practice that one appeals court has said violates the Fourth Amendment (and we think most Americans would agree).
In other words, assume no expectation of privacy.