Hi @Daniel Jepsen, welcome to the community!
It’s great that you want to get users to consent before you start sending them newsletters, I think that’s a good practice and to ensure high deliverability in the future.
However, it’s a bit tricky because technically they have not opted in (or have consented to your marketing) and soliciting them to join a newsletter in itself, might be perceived as such. Remember, the inbox providers can’t understand your intentions (even if its well meaning), they just look at the data that feeds into their algorithm. So if your request to join a newsletter is received poorly (ignored, or worse, marked as spam) - that is the reality you’ll have to deal with. Also, depending on your region, there may be rules and regulation on what type of emails you are allowed to send based on their consent.
The good news is, if they are current or past customers, there’s a high likelihood that they will visit your site, pay attention to what you say or do on social media, and engage or respond to your advertising. Use those tools to start getting them to opt-in!
What I recommend is use other avenues to get people to opt in - you can use a Klaviyo Signup Form (Popup) on your site, have incentives on a landing page for people to sign up, you can put links or reminders in your order confirmation emails or in your customer service email signature. Focus on building a clean and high quality List is better than the sheer number of emails you have access to.
As for “paying for unconfirmed clients” in Klaviyo’s pricing model - I understand the perception that if you’re not email people, you’re not using any resources - but Klaviyo is still collecting data and behavior information about those users that have not opted in. You can also still send “transactional emails” if you wish to in Klaviyo (depending on which ecommerce platform you’re on), and on the day they sign up, you’ll have a rich history of those users to build more segmentation and personalization. Also, at any time, you can delete them in bulk and remove them from Klaviyo if you wish to better manage your subscription tier.
Hope that helps!