Bateman's Bulletin, an electronic newsletter sent by Winnipeg South Centre MP Joyce Bateman's office on Friday evening, did not conceal the names or email addresses of those who received it.
Bateman's office issued an apology a few hours later, but some of the recipients say they are worried their privacy has been breached now that their addresses are exposed.
"When I started receiving messages from other people who had my email address … that's when the red flags went up and I realized how far-reaching this could really be," said Adelle Rempel, whose email address was visible in the email.
In a statement emailed to CBC News on Wednesday afternoon, Bateman apologized again for what she called an "administrative error."
"I take every opportunity to communicate with my constituents on matters that are important to them — be it job prospects, government investments and constituent accomplishments," she said.
"I apologize for this administrative error and have already put in place procedures to ensure it does not happen again."
Meanwhile, Rempel and some of the other recipients said they don't know how the MP got their email addresses in the first place.
Rempel said she plans to lodge a complaint with Manitoba's ombudsman.
"People can now just, you know, easily hack a system and find out what my taxes are, they could find out where I live. They could find out a lot of stuff that the government has access to," she said.
However, a spokesman for the provincial ombudsman's office told CBC News that provincial and federal privacy legislation do not apply to politicians.
A recent study for Canada's privacy commissioner noted that "Canadian federal privacy protection law does not cover federal political parties."