Hello - Lovely plugin!
A few times now, we have had an email sent to our subscribers when no new posts were published.
We are using Mailchimp Rss-to-Email and it works perfectly when we actually publish a post.
I'm wondering if something in your plugin considers a new PAGE being created, as a new post? I ask because yesterday I created a page, where I will show a certain category of posts, and this morning Mailchimp sent out an email.
Thoughts?