Cloudflare Workers MailChannels API
https://scrapbox.io/files/66352b9ffbc92a00239fff51.png
https://shinobiworks.com/blog/653/
https://zenn.dev/moutend/articles/6c527a5c0a348b
https://zenn.dev/takashikakizoe/articles/cloudflare-workers-hono-email-endpoint