(this post is a feed post from my comments on reddit)
r/Entrepreneur
Ask if the emails are double opt-in.
ask for examples of previous campaigns and references to other clients who have used them.
ask about the previous campaign –
* bounce rate
* open rate
* click through rate
* and if possible conversion rates
* ask for the estimate cost per conversion and cost per email open (these numbers can be used to compare with alternative channels costs)
* ask for the final number of click throughs
* ask for the final number of conversions
ask about GDPR or data privacy compliance
ask about email opt out and how thats handled.