Receiving email in a Cloudflare Worker is free. Sending from one via Cloudflare’s Email Sending requires the Workers paid plan — $5/month, $60/year, effectively a subscription for the ability to hit reply.
The workaround: inbound and outbound don’t have to be the same provider. Resend’s free tier covers 3,000 emails/month from your own verified domain — for a solo operator’s reply volume, effectively unlimited. Verify the domain, add the SPF and DKIM records (two minutes if your DNS is already on Cloudflare), and send over their HTTP API from the same Worker.
One detail that took care: replies must carry In-Reply-To and References headers or they arrive as new conversations instead of threading. Format them identically regardless of which provider sends.
Full setup: Free professional email on your own domain.