If you’re sending 80,000 emails at once, you’re doing something wrong. Studies show that 57% of people say getting too many emails from a sender will cause them to mark the content as spam. It’s best to send emails in smaller waves.
It’s the same idea with frequency, don’t flood their inbox with too many emails over a short period of time. They might unsubscribe. Make sure the emails you are sending are relatable or of interest to them.
As a guideline, if you are sending product adoption or upsell campaigns, you can send around 3 emails a week. If you’re sending customer acquisition campaigns, try and stick to only one email a week.
-Vendasta June 2019