For the people debating the "If it's bulk email, why not just use Mailchimp?" question, consider the Trello use case: Someone updates a ticket and there are 4 people subscribed for notifications. In that case, it sends the same email to 4 people.
According to the AUP, it's against the rules to send "emails directed to a number of individuals with the same content"
Are we really going to say that someone like Trello should be using Mailchimp for that?