Nylas CLI is a free, open-source command-line tool that connects your terminal to email, calendar and contacts across Gmail, Microsoft 365, Exchange, Yahoo, iCloud and IMAP. You authenticate once with an API key, then send mail over HTTPS without configuring SMTP, Postfix or provider SDKs. It ships with a built-in MCP server, so Claude Code, Cursor and other agents can read and send mail through typed tools. Built for developers scripting cron jobs, CI notifications and agent workflows.

• Email from the terminal: Read, search, draft, and send email across supported providers.
• Calendar management: Work with calendars and events through CLI commands.
• Contact management: Search and manage contacts from the terminal.
• MCP server: Connect email, calendar, and contact tools to compatible AI assistants.
• Agent Accounts: Create managed email identities for AI agents with their own inboxes and policy rules.
• JSON output: Return command results in JSON for scripts, automation, and command-line tools.
• Multiple providers: Supports Gmail, Outlook, Exchange, Yahoo, iCloud, and IMAP.
• Headless workflows: Designed to work from scripts, cron jobs, CI/CD pipelines, and AI agents.
• Cross-platform: Available for macOS, Linux, and Windows.
• Open source: The CLI is MIT licensed and available as an open-source project.

• Fast setup: nylas init creates an account, generates an API key and connects a test mailbox in one command. Most users are sending mail within a couple of minutes.
• Free and open source: The CLI itself costs nothing and the source lives on GitHub, so you can read exactly what runs against your mailbox.
• Automation-friendly: The same CLI can be used from terminal sessions, scripts, CI/CD workflows, and AI agent environments.
• Secure credential storage: API credentials are stored in the operating system's keyring rather than a plaintext configuration file.

• Steep learning curve: Reviewers find the documentation technical and hard to navigate, despite the large volume of guides. Expect some hunting for the right command.
• Overkill for simple jobs: If you only need to fire one email to one provider, msmtp or curl is lighter. The value shows up when you have multiple providers or agent workflows.
• Not designed for bulk sending: Nylas uses a connected-account pricing model rather than charging by email volume, making it less suited to high-volume broadcast email than services built around per-message sending.
• Costs scale by connected account: The CLI is free but the underlying platform bills per connected account. Enterprise quotes commonly reach four figures monthly, and reviewers report billing disputes and auto-renewal friction.

• Cron job and CI notifications: Wire deploy alerts or nightly report emails into a pipeline with one command. No SMTP relay to maintain and no app password to rotate when it expires.
• Scripted email testing: Spin up a mailbox in CI, run an assertion against a delivered message, then delete it. Repeatable, with no API client code to maintain.
• Multi-provider internal tooling: Build shared inbox or helpdesk tooling that treats Gmail, Outlook and IMAP accounts the same way, instead of writing three separate integrations.
• OTP and verification workflows: Send verification messages and retrieve one-time passwords from email with dedicated OTP commands. Custom metadata can also tag messages with application data for tracking and filtering.
• Calendar automation: Query free/busy data and create events from scripts, driving interview scheduling pipelines or syncing meetings into a CRM without exposing full event details.