Great!
The open rate of the email was 45,8%
That's excellent.
...and 27 people replied.
Oh. Oh dear.
~ 96% of respondents told that they would - or already have - recommended the tool for a friend or colleague.
96% of the people who are enthusiastic enough about the service to respond to an email would recommend the service, but the 97.8% of people didn't respond is by far the more important number. If the people who'd tried the app were a random sample of the population then 2.2% might be enough to suggest there's a valid premium business model there, but the people who tried the service weren't randomly selected - they were a self-selected group of people who are interested enough in user testing to sign up for the service. If you can't get a significant response from a group who are (alledgedly) interested in your type of product then you clearly have a big messaging problem.