Hey @dave_donoghue, I don't think subscribers will mark your email as spam as this still depends if they really subscribed from you as well as the content of your email/newsletter. Here are some articles that can help you improve your deliverability:
- 9 steps to improve email deliverability 7
- Deliverability 1013
- Sender Reputation: Your Role in Improving Your Deliverability 4
- Why Is My Subscriber Showing As Complained? 5
- How’s your email reputation? 6
I hope these help but you can always reach out to our support team at help@convertkit.com4