I don't think I agree about massive market. There's a large # of newsletter publishers that don't advertise. Thing of every SaaS newsletter promoting their ow

I don't think I agree about massive market. There's a large # of newsletter publishers that don't advertise. Thing of every SaaS newsletter promoting their own sales, Best Buy and their newsletters, Groupon doesn't directly advertise (this distinction is somewhat complicated). Selling ads appropriately is also extremely difficult. Click-thru rates is another issue, but I could probably overcome this issue with unsubscribe rates data from easyunsubscriber after it finds P/M fit. I don't think a lot of this stuff is public unless SendGrid/MailChimp/et al has open APIs which I doubt. I think publishers often fudge this data and if their open rates are bad, they inflate the numbers of don't mention them. Very difficult to monitor esp. since the data isn't open. Do you advertise in newsletters or publish one? I'd love to hear more of your experiences.