“Take a whiff of this.”

Jay Stuart DeVaughn wrote those words on 26 letters mailed to President Obama, private citizens and foreign embassies. Several of the letters, most mailed in 2009, included rants about health-care reform — and all included a suspicious powder.

DeVaughn was sentenced to six years in federal prison for the incidents, which, although no one was harmed, raised the obvious specter of another anthrax attack.

A decade ago, anthrax spores delivered in letters killed five people, injured 17 and changed how the U.S. Postal Service and other institutions think about mail safety.

The 10th anniversary of the attacks, the debate over testing an anthrax vaccine on children and such incidents as the DeVaughn case may put the threat of such bioterrorism back in the news, but for many — even some postal workers — the issue’s immediacy has faded.

“Most people, I think, have forgotten about anthrax in the mail,” Postmaster General Patrick R. Donahoe said. “And truthfully, that’s probably not a bad thing.”

The Postal Service has been more focused on its very existence, as mail volume continues to fall and it loses billions of dollars.

But how safe is the mail?

The Postal Service now relies on both human checks and machine screenings to track suspicious mail, it says. With tens of thousands of postal facilities to protect, the U.S. Postal Inspection Service has responded to more than 52,000 calls about suspicious mail since 2001, it said, and inspectors respond to about 10 calls daily. Most, they said, are false alarms.

Shift supervisors receive regular updates on evolving threats, and postal inspectors practice regularly with local law enforcement agencies in anticipation of an attack.

But mail was used as a weapon long before anthrax.

Historically, cases of dangerous mail are spawned by personal disputes between jilted lovers or feuding neighbors, inspectors said. In 1952, for example, a woman was arrested after she mailed a box of cyanide-laced Bon Bon Caramels to her estranged husband. He was suspicious and alerted authorities.

Before anthrax, the most high-profile mail scare involved Theodore Kaczynski — dubbed the Unabomber — who over nearly 20 years killed three people and injured 23 with mail bombs before he was arrested in 1996.

Two years ago, inspectors arrested a West Virginia man for mailing an improvised explosive device to a former neighbor in Minnesota. He’s serving 2½ years in prison.

And an unsolved case from January still puzzles officials: Two packages with incendiary devices delivered to Maryland government buildings flashed when workers opened them. The next day, a similar package addressed to Homeland Security Secretary Janet Napolitano ignited at a District of Columbia postal facility.

The exploding packages “took employees back to anthrax and the evacuations back in 2001,” said Dena Briscoe, president of the local chapter of the American Postal Workers Union, who spends time consoling colleagues still rattled by the anthrax deaths of postal workers Joseph P. Curseen and Thomas L. Morris Jr.

After the device ignited in the District in January, “the people in the area where it happened were told to go into a break room,” Briscoe said. “Then the people in the back area of the building, they didn’t even know that this was going on. Nobody was told to get out.”

Still, Briscoe said, most workers are less nervous about attacks — and many don’t wear the gloves and masks provided as a precaution.

Anthrax was something the Postal Service had never anticipated, postal officials said.

“We didn’t know how to handle it,” said Guy J. Cottrell, chief of the Postal Inspection Service. “But we’ve made a lot of changes to how we respond to incidents and how we educate our employees if they see a potential threat.”

Employees are trained to be on the lookout for envelopes without a return address, an invalid Zip code, or weird or scribbled jargon. Sharp objects protruding through boxes or dust or liquids leaking from envelopes is also a potential threat. Questionable pieces of mail are supposed to be turned over to inspectors for further screening.

The USPS spends $101 million annually to screen every piece of first-class mail sent or received by U.S. households and mail sent to federal addresses in Washington.

Here’s how it works:

At the nation’s more than 200 mail-processing facilities, as envelopes travel along conveyor belts to be scanned and bar-
coded, a machine about the size of an office copier takes periodic air samples to track for biological agents. The machine can test about 36,000 pieces of mail an hour, inspectors said.

Those machines have not detected any harmful biological chemicals since 2002, when USPS began using them, inspectors said.

Magazines, catalogues and such mail as credit card solicitations are not screened further because the USPS considers the senders trusted sources, inspectors said. Priority Mail and Express Mail packages — which require return addresses and tracking numbers and must be dropped off in person or handed to a letter carrier — are not run through biological detection machines, because threat assessments have deemed such inspections unnecessary, inspectors said.

Mail destined for the White House, Congress or federal agencies require closer scrutiny. Several letters with white powder were delivered to Capitol Hill during the anthrax scare, and lawmakers, Obama and Cabinet secretaries remain a target of copycat attacks.

Once mail with federal addresses is sorted at a Washington facility, USPS trucks it to a New Jersey irradiation facility operated by Sterigenics, a company known for its medical sterilization equipment. The Postal Service said it spends about $12 million annually on irradiation but declined to comment further, citing security concerns.

But a 2008 Government Accountability Office report details what happens in New Jersey: The mail sent to federal addresses in Washington is heated to temperatures often exceeding 150 degrees. Large containers holding first-class mail and packages are scanned by a high-energy electron beam or X-rays to kill potentially harmful biological agents, including anthrax, the GAO said. The process delays the delivery of federal mail for two to three days.

The USPS irradiated about 1.2 million containers of government mail between 2001 and 2008, according to the GAO. That amount has dropped significantly in recent years with the government’s embrace of the Internet.

Postal inspectors did not dispute the GAO’s findings.

Although he is focused mostly on the Postal Service’s fiscal woes, Donahoe, who spoke at services marking the 10th anniversary of the attacks that killed the postal workers, said during an interview that the episode still haunts him. “We have people who are still suffering,” he said.

And what was the substance in DeVaughn’s letters? The white powder, inspectors said, was coffee sweetener.