Missing subscribers on Jetpack

I recently switched from using Jetpack to send posts to followers, to an external email service. (I downloaded the CSV of subscribers and then transferred them across).

Since then many people have told me that they are no longer receiving emails. I thought this must have been a problem with the new program. But it turns out their email addresses were not in the Jetpack list of subscribers or on the CSV file to begin with – even though they were previously receiving emails.

So I’m thinking there must be some kind of separate list or group of email addresses that I can’t access. Any idea what the problem might be and how I can access those missing addresses?

The website is http://www.theshovel.com.au
Thanks for your help