Unfortunately, the Mailchimp license is CC Share-alike, which means that the derived material based upon it should be licensed under the same license or in a equivalent one. For code, the equivalent type ("copy-left" type) would be the GPL.
So, this boilerplate can't be MIT.
I noticed in the e-mail template, that some parts of the code are based on The MailChimp Reset.
Unfortunately, the Mailchimp license is CC Share-alike, which means that the derived material based upon it should be licensed under the same license or in a equivalent one. For code, the equivalent type ("copy-left" type) would be the GPL. So, this boilerplate can't be MIT.