I would also suspect Edison mail.
Their privacy policies are less then ideal:
We process emails collected through the Services to identify those related to commercial activities, such as subscriptions, sign-ups/cancellations, account requests and confirmations, purchases, travel, reservations, event tickets, boarding passes, promotions, bills, and package shipments (and including emails you set up to auto-forward from another email account). We refer to this data as “Commercial Data.”
Maybe time to use something different like Bluemail, or even better use the inbuilt Apple mail client.