Hi Roland, to answer your question:
When we talk about "109,239 emails", we actually mean email campaigns, of course. (The size of the recipient list cannot be detected by us.) The 3-month timeframe of our study covers 12,86 weeks; therefore, the 4,166 ecommerce companies we looked at on average sent out 2.04 campaigns per week. If we just examine the subset of 3,711 companies that used a professional email service provider, the average number of campaigns sent out per week is 2.3.