Why is it so expensive to send an email?

The piece investigates why bulk email services charge far more than the apparent cost of sending a network request. The author builds a basic email sender in Haskell using OpenSSL and finds that the mechanics are manageable: SMTP is a text-based exchange, and a message can be sent with ordinary TCP connections. But SMTP’s original design lets senders claim any identity, so modern delivery also requires domain-authentication measures, including DNS records that publish cryptographic information. After configuring these, the author can send messages that reach Gmail, yet the same messages fail to appear even in Outlook’s spam folder. The technical work is not the main obstacle; getting inbox providers to accept the mail is.

The central argument is that email delivery depends on reputation, which differs across providers and can be judged by domain, individual IP address, or even a broader IP address block. A small cloud-hosting customer may share a block with other senders, so someone else’s spam can damage its ability to deliver legitimate messages. Reliable access across many inbox services may therefore require a dedicated IP block and enough daily email volume to establish and maintain a good reputation. The author’s conclusion is that paid email services charge not because sending the message itself is difficult, but because they operate the infrastructure and build the trust needed to navigate inconsistent, evolving spam filters.