Always Ask for MailChimp Newsletter Reconfirmation Outside of MailChimp
When you want to merge newsletters in MailChimp like I do and tell your subscribers to sign up at the new list and unsubscribe from the old to not receive any notifications – then you’re setting yourself up for trouble! Because it turns out that mass-migrations from list A to list B mostly register as mass unsubscribes from list A. And an unsubscribe rate of 9% or higher (I don’t know the actual minimum value, but 9.23% triggered it for my account) will automatically up the risk level of your whole MailChimp account.