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Qasim Muhammad
Qasim Muhammad

Posted on • Originally published at cli.nylas.com

Best CLI Email Tools Compared: mutt vs mailx vs msmtp vs Nylas CLI

#cli #devops #linux #tutorial

You want to send email from a script. Or read your inbox without leaving the terminal. Or automate calendar invites from a cron job.

The Unix ecosystem has tools for this — mailx, mutt, msmtp, swaks — but each one covers a different slice of the problem. None handles modern OAuth for Gmail or Microsoft 365 out of the box. None outputs JSON for scripting. None touches calendar or contacts.

Here's how they compare, and where Nylas CLI fits in.

The five tools

mailx (BSD Mail / Heirloom mailx)

The classic Unix mail command, standardized in POSIX.2. Available on virtually every POSIX system. Sends via local MTA or SMTP relay. Simple but limited: no OAuth, no JSON, minimal attachment support.

echo "Build failed" | mailx -s "CI Alert" dev@example.com
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mutt / NeoMutt

A powerful terminal mail client with a full TUI. Supports IMAP, POP3, SMTP, GPG, and extensive .muttrc customization. Excellent for power users who want to read mail interactively. Less suited for scripting.

mutt -s "Report" -a report.pdf -- team@example.com < body.txt
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msmtp

A lightweight SMTP client that acts as a sendmail replacement. Does one thing well: relay messages to an SMTP server. Supports TLS and multiple accounts. No reading, no IMAP, no search.

echo -e "Subject: Test\n\nHello" | msmtp recipient@example.com
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swaks (Swiss Army Knife for SMTP)

A purpose-built SMTP testing tool. Lets you craft raw SMTP sessions with full protocol control. Perfect for testing mail server configs and debugging delivery.

swaks --to test@example.com --server smtp.example.com --tls
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Nylas CLI

A modern CLI that connects to Gmail, Outlook, Exchange, Yahoo, iCloud, and any IMAP provider through OAuth. Provides email, calendar, and contacts in one tool. JSON output for scripting. Built-in MCP server for AI agents.

brew install nylas/nylas-cli/nylas
nylas auth login
nylas email send --to alice@example.com --subject "Hello" --body "From the CLI"
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New to it? The getting started guide takes under a minute.

Feature comparison

Feature mailx mutt msmtp swaks Nylas CLI
Send email Needs MTA Needs SMTP Yes Testing only One command
Read inbox Local only Yes (TUI) No No Yes
Search email No Basic No No Full-text
Gmail OAuth2 No Complex setup No No Built-in
Microsoft 365 No Complex setup No No Built-in
Yahoo/iCloud No No No No Built-in
JSON output No No No No --json
Attachments Limited Yes No Limited Yes
GPG sign/encrypt Manual Built-in No No Built-in
Calendar access No No No No Yes
Contacts No No No No Yes
AI agent (MCP) No No No No Built-in
Smart compose No No No No AI-powered

When to use which

Use mailx when you need to fire off a quick notification from a cron job on a system where Postfix or sendmail is already configured. It's everywhere and requires zero setup.

Use mutt when you want to read, organize, and reply to email interactively in your terminal. It's the Vim of email clients — steep learning curve, unmatched power once you know it.

Use msmtp when you need a lightweight sendmail replacement. Pair it with mutt or mailx for a complete setup. Great for systems that need to relay mail without a full MTA.

Use swaks when you're debugging SMTP delivery, testing SPF/DKIM/DMARC configurations, or verifying mail server connectivity. It's a diagnostic tool, not a daily driver. For more on email deliverability debugging, see SPF, DKIM, DMARC: Debug Email Deliverability from the Terminal.

Use Nylas CLI when you need multi-provider OAuth (Gmail, Outlook, Exchange, Yahoo, iCloud, IMAP), JSON output for scripting, calendar and contacts alongside email, or AI agent integration via MCP.

Quick examples with Nylas CLI

Send email (any provider) 

nylas email send \
  --to "colleague@company.com" \
  --subject "Quarterly report" \
  --body "Please review before Friday." \
  --yes
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Full guide: Send Email from the Command Line

List and search inbox 

nylas email list --unread --limit 10
nylas email search "invoice" --json | jq '.[].subject'
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Provider-specific guides:

Calendar management 

nylas calendar list --limit 5
nylas calendar create --title "Standup" --when "tomorrow 10am" --duration 30m
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Full guide: Manage Calendar from the Terminal

Give AI agents email access 

nylas mcp install --assistant claude-code
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One command gives Claude Code, Cursor, or Codex full email and calendar tools via MCP. Setup guide: Give Your AI Agent an Email Address

Extract OTP codes 

nylas otp get
# => ✓ Found code: 847291 (copied to clipboard)
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Full guide: Extract OTP Codes from Email

GPG encrypted email 

nylas email send --to legal@partner.com --subject "Contract" --body "..." --sign --encrypt
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Full guide: GPG Encrypted Email from the CLI

PowerShell support

All commands work in PowerShell too. Dedicated guides:

Full comparison with code examples for each tool: Best CLI Email Tools Compared

Related guides:

All guides: cli.nylas.com/guides

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