Field notes from the engineers building email security at Mailprotector.https://mailprotector.engineering/en-ushttps://mailprotector.engineering/articles/slow-tls-handshake-jammed-the-queue/https://mailprotector.engineering/articles/slow-tls-handshake-jammed-the-queue/One destination's mail server stopped finishing its TLS handshakes. Because of a timeout we'd set in the wrong place, that was enough to back up delivery for everyone.Thu, 28 May 2026 00:00:00 GMTPostmortemSMTPInfrastructurehttps://mailprotector.engineering/articles/testing-a-mail-server/https://mailprotector.engineering/articles/testing-a-mail-server/Our test suite spends most of its effort pretending to be badly behaved senders. Here's how we fake the rest of the internet on a laptop.Sat, 23 May 2026 00:00:00 GMTTestingHow We WorkSMTPhttps://mailprotector.engineering/articles/helo-world/https://mailprotector.engineering/articles/helo-world/Why a company that moves email for a living is starting an engineering blog, and what we plan to put here.Mon, 18 May 2026 00:00:00 GMTMetaSMTP