Am I misunderstanding the limitations of which services are available to use for “bring your own SMTP”?
Fertit is designed to work with newsletter-appropriate SMTP services like SendGrid, Mailgun, Amazon SES, Postmark, and Mailjet - providers that explicitly support bulk email sending. These typically cost $10-50/month depending on volume, which is still much cheaper than the $79+ full-service ESPs charge. The value prop is: instead of paying ConvertKit $79/month for 1000 subscribers, you pay SendGrid ~$15/month for SMTP + Fertit $9.99/month = ~$25/month total, while still getting proper unsubscribe handling, preference management, and basic compliance features.
You're right that it requires users to handle the SMTP setup themselves - it's positioned for people who want more control and cost savings but don't need the full white-glove deliverability management of premium ESPs.
Thanks for pointing this out - I should make the SMTP requirements clearer in the marketing!
https://postmarkapp.com/transactional-email
This entire link describes their definition of transactional email.