Email is how most files still move between people: the signed contract, the PDF invoice, the logo embedded in a newsletter. If your app sends or processes mail, it has to handle attachments, and doing that against each provider means Gmail's attachment encoding, Microsoft Graph's, and raw MIME for IMAP. The Nylas Email API gives you one model for both directions: attach files to outbound messages with the same call you use to send, and pull files off inbound messages with a read-only Attachments API.
This post covers both halves from two angles: the HTTP API for your backend, and the nylas CLI for the terminal. I work on the CLI, so the terminal commands below are the ones I reach for when I'm checking a file came through.
Two APIs: one to attach, one to read
There's a split worth understanding up front. You add attachments through the Messages or Drafts API, as part of sending or saving a message, and you read existing attachments through the dedicated Attachments API. The Attachments API is read-only: it downloads bytes and returns metadata, but it never adds files. That division keeps the model simple, since attaching is part of composing a message and reading is a separate concern.
