[ad_1]
Hi, about the report of old subscriptions I really don’t know, it sounds like some system is scanning old emails and triggering the confirmation links on them… just a hypotesis.
About the delivery problem, it surely related to your provider probably blocking the emails when too many are sent. With 20k email I acn suggest a professional service to deliver, like Amazon SES, Sendgrid, …. With them you have tools to setup the DKIM, SPF and DMARC in the correct way: they’re becoming mandatory by Google and Yahoo.