The Republican nominee cried foul after learning about the law enforcement bureau's decision.
At a rally in the Detroit suburbs, Mr Trump insisted it would have been impossible for the FBI to review what has been reported to be as many as 650,000 emails in such a short time.
"Right now she's being protected by a rigged system. It's a totally rigged system. I've been saying it for a long time," he told supporters in Sterling Heights, Michigan.
Media captionUS Election 2016: Which countries have already had female leaders?
"Hillary Clinton is guilty, she knows it, the FBI knows it, the people know it and now it's up to the American people to deliver justice at the ballot box on November 8."
While Mrs Clinton herself did not address the FBI director's letter on the trail, her campaign said it was always confident she would be cleared.
Image captionFBI Director James Comey's latest letter
In Manchester, New Hampshire, on Sunday, she said the country was facing "a moment of reckoning" and Americans must choose between "division and unity".
In July, the FBI said she had been "extremely careless" to handle classified material on a private email server as secretary of state from 2009-13, but it had found no evidence she committed a crime.
However, 11 days before the election, FBI director James Comey had pitched the race into turmoil by announcing a newly discovered batch of Clinton emails would be investigated.
The bombshell infuriated the Clinton camp, but threw a lifeline to a Trump campaign that had been receding in the polls.
Analysis - Anthony Zurcher, BBC News, Washington
It was much ado about nothing, but it certainly amounted to something. While FBI Director James Comey, in effect, said "never mind" with regards to Hillary Clinton's emails, for the past two weeks the story has dominated the political conversation, and Democrats have paid a price.
While Mrs Clinton's presidential hopes have stabilised, talk of a possible rout - and sweeping down-ballot victories in congressional races - are a distant memory.
Mrs Clinton will now try to focus on her closing campaign message. Donald Trump will continue to accuse his opponent of corruption and, perhaps, again allege the FBI is covering for her.
On the eve of voting, the dust kicked up by this story won't have fully settled by the time Americans head to the polls.
Once this election is over, there should be serious soul-searching within the FBI and the media about how this saga played out. The nation's top law-enforcement agency was a source of constant leaks, as internal disputes spilled into public view.
If Mr Trump wins, many on the left will blame Mr Comey for the result. If Mrs Clinton prevails, she likely will bear a lasting grudge over this political near-miss.
In a letter to Congress on Sunday, Mr Comey said his investigators had "worked around the clock" on the latest emails, which were found in early October in a separate investigation.
The messages reportedly turned up on a laptop belonging to the estranged husband of one of Mrs Clinton's closest advisers, former congressman Anthony Weiner, who is accused of sending illicit messages to a 15-year-old girl.
Mr Comey said investigators had found no reason to change the FBI's earlier assessment that Mrs Clinton should not be charged for her handing of classified information.
Image copyrightAPImage captionHillary Clinton will hold a star-studded rally on Monday evening
Government officials told US media that investigators had established the newly found emails were either personal, or were duplicates of correspondence they had previously reviewed.
Senate Democratic leader Harry Reid said Mr Comey's conclusion "underscores the irresponsibility" of the law enforcement chief's notice late last month to Congress about Mrs Clinton.
Both candidates are set for a whistle-stop tour of battleground states on Monday, in a last-ditch dash for votes.
Mrs Clinton starts the day in Michigan, a traditional Rust Belt, Democratic stronghold that has been heavily targeted by Mr Trump in recent days.
Image copyrightEPAImage captionNearly 42 million early voters like these in Los Angeles have already cast ballots
She will then head to Philadelphia where she will be joined by President Barack Obama, First Lady Michelle Obama, husband Bill Clinton and Bruce Springsteen.
The Democratic candidate will end her White House campaign with a midnight "get out the vote rally" in North Carolina.
Mr Trump heads to Florida, North Carolina and Philadelphia before ending with a rally in Grand Rapids, Michigan.
In states where early voting is allowed, nearly 42 million Americans have already cast ballots in the presidential election.
They have turned out in record numbers in crucial battlegrounds such as Florida, North Carolina and Nevada.
An estimated 126 million voters cast ballots in the 2012 White House election.
Media captionThousands rallied in Seoul calling for the president to step down
South Korean prosecutors have issued arrest warrants for two former aides of President Park Geun-hye as part of an investigation into government corruption.
Ms Park's former senior secretary for policy Ahn Jong-beom, and private secretary Jung Ho-sung, are wanted in relation to charges of fraud and abuse of power.
The president has so far refused to resign over the scandal.
She apologised on TV on Friday.
Appearing close to tears in a televised address, Ms Park admitted that she made an error in allowing her friend Choi Soon-sil inappropriate access to government policy-making.
But she denied allowing cultish rituals to be performed in the presidential palace.
Ms Choi, the daughter of a cult leader, is suspected of using their friendship to solicit donations to a non-profit fund she controlled. She is in detention facing charges.
Image copyrightGETTY IMAGESImage captionSouth Korean President Park Geun-hye apologised over the scandal in a televised address
The corruption scandal, which threatens to engulf Ms Park's leadership, has left the president with an approval rating of just 5%, the lowest ever for a sitting South Korean president.
Both candidates have been making late changes to their travel schedules as falling poll numbers for Mrs Clinton in some key Democratic-leaning states present what the Trump campaign sees as new opportunities.
However, a new NBC/Wall St Journal opinion poll on Sunday suggested a four-point lead for Mrs Clinton.
The latest Washington Post/ABC tracking poll puts her lead at five points.
Sunday's campaign stops take Mrs Clinton to Ohio, Michigan, Pennsylvania and New Hampshire, while Mr Trump travels to Iowa, Minnesota, Michigan, Pennsylvania and Virginia.
'There is no gun'
On Saturday evening, Mr Trump had stopped speaking at the Reno rally after seeing something in the auditorium.
He was grabbed by two agents, who rushed him off stage, while the protester was held down and searched.
Media captionMrs Clinton was joined by Katy Perry as she urged the crowd to vote for "a better, fairer, stronger America"
The Secret Service later confirmed that someone in front of the stage had shouted "gun", but that "upon a thorough search of the subject and the surrounding area, no weapon was found".
Austyn Crites, the man at the centre of the disturbance, said he was attacked when he brought out his sign.
"I keep repeating - I'm down, someone is trying to choke me - and I'm saying to these people; 'There is no gun, I just have a sign'," Mr Crites explained after the incident.
Media captionAustyn Crites said he told the crowd "there is no gun - I only have a sign"
For a moment here in Reno, a political campaign simmering with tension and bubbling with resentment boiled over. As shouts of "gun" rang out and Donald Trump was hustled from the stage there was panic at the front of the packed hall. Some people dived to the floor, others ran for the exits.
A few journalists who left the media pen and headed towards the commotion were treated to manhandling and verbal abuse. There was no gun, of course, and the drama quickly subsided.
Drowned out by the commotion was an allegation of ballot-rigging which Mr Trump had made a few minutes earlier. The Republican claimed that some early voting stations in Nevada had been kept open "for hours and hours beyond closing time" to allow Democratic voters to be brought in by bus.
It was a reminder that this election is already well under way. More than 40 million Americans have voted early. In states which can provide a path to the White House, the data suggests that Hillary Clinton has the edge. But history is littered with errant polls and, as we saw today in Reno, unpredictable events.
Hillary Clinton's chief strategist, John Podesta, said on Sunday that she would focus on Nevada and Michigan, adding that if she won those two in particular, "Hillary Clinton is going to be the next president of the United States."
Mr Podesta also accused Mr Trump of being an advocate of Russian foreign policy and rejecting the bipartisan US approach.
Republican vice-presidential candidate Mike Pence told Fox News Sunday that Mr Trump would accept a clear outcome of the election, although he reserved the right to challenge disputed results.
In the final TV debate with Mrs Clinton, Mr Trump had refused to commit to accepting the result if he lost.
'Tuesday will be fun'
On Saturday evening, Mrs Clinton appeared with Katy Perry at a rally in Philadelphia, Pennsylvania, where the Democratic presidential candidate urged the crowd to vote.
"When your kids and grandkids ask you what you did in 2016," Mrs Clinton said, "I want you to be able to say, I voted for a better, stronger, fairer America."
Perry, who took to the stage to sing the song Nasty, said she was looking forward to election day. "Tuesday's going to be fun," she said, "but Wednesday is going to be better".
Media captionDemocratic VP pick Tim Kaine jams with Jon Bon Jovi in Florida
Mrs Clinton has seen her lead slip following last week's FBI announcement that it was looking into emails that may be connected to her use of a private email server while she was secretary of state.
More than 40 million early voters have already cast their ballots. Reports suggest many more Latino voters are turning out early in battleground states including Florida, Arizona and Nevada compared to past elections.
Donald Trump told a rally in Tampa, Florida, on Saturday he was "going into what they used to call Democrat strongholds, where we're now either tied or leading. We're going to Minnesota, which traditionally has not been Republican at all".
Media captionUS election: Voters voice worst-case scenarios
Pennsylvania and Michigan are also both on his agenda and they too have been tough states for Republicans. They have not won them since 1988.
Florida is an important state, particularly for Mr Trump, with many seeing it as a must-win. Candidates need 270 electoral college votes to win the presidency. Florida is worth 29 and polls suggest the contest is tight.
ERIN STUMP
ERIN STUMP
