What is an appropriately-sized email list?
The size of your email list matters and it will determine how many emails you send per person in a certain span of time. Like with email open rates, the size of your email list should ultimately depend on your industry, as well as the size of your business.
The size of your email list should take into account not only the average open rate as an email marketing benchmark, but also the conversion rate. The average conversion rate is around 3 percent. No matter how big your business is, however, you should strive to have at least 1000 to 2000 active subscribers. The more the better.
If this number is any lower, you run the risk of having a too-low number of conversions. On average, half of your email list subscribers will be interested in your product or services, while the other half is less so.
Email marketing, identified visitors and email averages can be found, here.