What are the legal ramifications of accidently sharing email addresses in Canada?
What legal ramifications are you expecting to potentially befall you? The OP’s list might reveal names of people taking a form of medication. The reveal might intrude on people’s privacy. On a lesser note, the reveal might leave them open to spamming. The first two are particularly volatile. Imagine for a moment that all people on the list are taking medication for a condition best kept private. Imagine as well people who are account holders for a particular bank and whose email address is now revealed. This slipup can open the company to all sorts of legal trouble.
Do we need to worry about the legal ramifications of these completely unintentional events? The legal ramifications are nil. Consider two things: 1.) there is probably no clear legislation outlawing what is essentially emailing people, and 2.) in order for someone to bring suit, they would have to show damage. I doubt either of these applies. Even in Canada.