Some workers say their new duties can't be completed in a regular eight-hour workday and they feel pressured to do the extra work for no pay.
Postal worker Mars Bazrafshan said many of his colleagues have given up claiming overtime.
"There are lots of people that will work due to they have mortgages to pay, they have loans, they just want to keep quiet. Let's just go do the work … extra work without pay, yeah, they do that," he said.
Gary Capobianco, a letter-carrier in downtown Toronto, said many workers fear they'll lose their jobs if they book their overtime, and that Canada Post knows it.
'Grievances procedure is broken'
"I see it as an extortion racket, where Canada Post says to you, 'You want protection, we'll give you protection. All we're asking for is your overtime pay.' They don't say it, it's not explicit, but that's what's going on. And a lot of people make that deal with Canada Post."
Bazrafshan said he's an example of why they might feel that way. He's in the process of being dismissed after years of disciplinary actions he said began because he was scrupulous about claiming his extra time.
He said he has few avenues to get redress.
"We cannot raise our voices [any way other than] grievances and that grievances procedure is broken," he said.
Backlog of 50,000 grievances
Canada Post admits it has a backlog of about 50,000 grievances for 52,000 unionized members. More than 700 are dismissal cases.
"There are a large number of grievances. … We apply the resources we can to that," said Jon Hamilton, a spokesman for Canada Post, adding workloads are carefully calculated to take up to eight hours.
"If somebody is consistently using overtime for something that we've managed and measured to be eight hours then you've got to investigate that," he said.
Canada Post is having to adjust to a steep decline in letter mail, Hamilton said, and the process has been stressful for everyone.