uppermillwill

I am sure these are good improvements for future users.

I question why anyone would want an email to be sent to every customer that has ordered in the past (one email for every order) just because you have run the retrospective apply process.

I was running this to see how many people would get rewards (and how many rewards each) in order to validate if the reward I had suggested was worth it. I was planning on running a number of scenarios of different types of reward option to see what was the best option – there was no expectation (or warning or documentation) that this was going to send emails, why would it do that?

I’m sorry but your response and lack of concern for my business is not acceptable.

You have no safeguards in place before emails are sent.
You have a plugin that forces you to set up a program to even view the settings which then means anything else you do may well trigger emails.

There may well be things I could have done differently but I have to say that after more than 10 years of working on WordPress on hundreds of websites and using thousands of plugins, I haven’t come across an issue like this.

I have come across bad plugins before that didn’t do what they said, but not one that at first glance seems quite well documented but after less than 5 mins into working with it, it causes a massive issue.

There are several obvious safeguards you can and should apply to your plugin. I would list them but I am to busy dealing with the fall out from the catastrophic problem your plugin has caused.