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Notes on software and email systems by Pedro Paiva, starting with an email learning series.

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• An email lab: experiments for understanding delivery

  October 13, 2026

  Run five controlled investigations and record what each observation actually establishes.

• Building reliable email workflows in an application

  October 12, 2026

  Use durable email intents, explicit send attempts, and authenticated events to recover from failures.

• Email transport security: what TLS protects

  October 11, 2026

  Distinguish individual encrypted hops, validated submission, and policies for server-to-server TLS.

• DMARC: connecting authentication to the visible sender

  October 10, 2026

  Apply the updated DMARC standard to alignment, policies, reports, and a careful rollout.

• DKIM: how an email carries a verifiable signature

  October 9, 2026

  Read a DKIM signature, find its public key, and understand what verification proves.

• SPF: which servers are allowed to send for a domain?

  October 8, 2026

  Evaluate SPF identities, mechanisms, forwarding failures, and lookup limits.

• Accepted, delayed, bounced: understanding email delivery outcomes

  October 7, 2026

  Use delivery timelines and status codes to distinguish acceptance, retry, and permanent failure.

• Inside an email: MIME, HTML, attachments, and encoding

  October 6, 2026

  Inspect MIME alternatives, attachments, inline images, and encodings in a saved message.

• How DNS tells email servers where to deliver a message

  October 5, 2026

  Read MX preferences, address lookups, null MX, and DNS failures without guessing mailbox validity.

• Email envelopes and headers: why there is more than one sender

  October 4, 2026

  Separate the displayed sender, reply destination, and delivery-failure address.

• An SMTP conversation, step by step

  October 3, 2026

  Follow a welcome email through the conversation between mail servers, from the first greeting to final acceptance.

• How email works: the components behind a message

  October 2, 2026

  Meet the clients, servers, and mailboxes behind a welcome email.

• What happens after my application sends an email through AWS SES?

  October 1, 2026

  Follow a welcome email through SES, from the first API response to the receiving server and the delivery events our application needs.