Madam Speaker, the protection of Canadians' personal information is a priority for the CRA. Individuals signed up for My Account alerts may receive a notification from the CRA indicating that their email address has been removed from their account. This step is taken proactively by the CRA as a security precaution. Let me be clear that there was no breach of CRA systems. Those affected by this measure can expect a letter by mail with instructions on how to unlock their accounts in the coming days.
In the House of Commons on February 19th, 2021. See this statement in context.