Sendmux Attachments

Q: What is a Claude Code skill and how does the Sendmux Attachments skill fit in?

A Claude Code skill is a SKILL.md file that lives under ~/.claude/skills/<name>/ and tells the Claude Code CLI agent how to perform a specific task (instructions, prompts, allowed tools). Skills are auto-discovered at session start. Sendmux Attachments is one of 67,000+ skills indexed in the open ClaudSkills catalog, classified under the Product category. Learn more at https://claudskills.com/learn/what-is-skill-md/.

Category: Product · Sub-category: ux-research · Last updated: 2026-07-11

Use Sendmux attachment workflows without wasting model context on base64. Use when uploading, downloading, reading, forwarding, or sending email attachments through Sendmux MCP, CLI, SDKs, or direct HTTP, especially when choosing file_path vs presigned upload URL vs inline base64, reading inbound attachments with mailbox_read_attachment, fetching short-lived download_url links, or attaching local files to outbound mail.

Security AStatic scan found no risk patternsHow grading works ›

From the source SKILL.md

Use this skill whenever a Sendmux task involves attachment bytes.

What this skill does

Sendmux Attachments is a community-contributed Claude Code skill in the ux-research sub-category. It ships as a SKILL.md file that Claude Code auto-discovers under ~/.claude/skills/sendmux-attachments/ and loads when your prompt matches the skill's trigger.

When to invoke it: Use when uploading, downloading, reading, forwarding, or sending email attachments through Sendmux MCP, CLI, SDKs, or direct HTTP, especially when choosing file_path vs presigned upload URL vs inline base64, reading inbound attachments with mailbox_read_attachment, fetching short-lived download_url links, or attaching local files to outbound mail.

Who uses this skill

The Sendmux Attachments Claude Code skill is built for product managers, product designers, and cross-functional teams planning, shipping, and measuring product features. It's part of ClaudSkills (also referred to as Claude Skills or Claude Code Skills) — the open community-curated registry of 149,000+ SKILL.md files for Anthropic's Claude Code agent and the wider Claude ecosystem (Claude API, Claude Agent SDK).

How to install

Free

Manual install (2 steps)

mkdir -p ~/.claude/skills/sendmux-attachments
curl -L https://claudskills.com/skills/sendmux-attachments/SKILL.md \
  -o ~/.claude/skills/sendmux-attachments/SKILL.md

Or just download SKILL.md directly and drop it into ~/.claude/skills/sendmux-attachments/. Claude Code auto-discovers it on next session.

Skills live at ~/.claude/skills/sendmux-attachments/SKILL.md on macOS/Linux, or %USERPROFILE%\.claude\skills\sendmux-attachments\SKILL.md on Windows. See the full install guide for step-by-step instructions.

📱 Install from your phone or desktop Telegram

Open @claudskills_bot on Telegram, tap Open Desktop App, and the desktop app installs this skill for you. Or share the bot link with a colleague — they get the same one-tap install. Learn more →

Pro

One-click install via the desktop app

The ClaudSkills desktop app installs any skill directly into ~/.claude/skills/ with one click — no terminal required. Pro starts at $9/mo or $149 lifetime.

Pro

For the full experience including quality scoring and one-click install features for each skill — upgrade to Pro.

See pricing → Download desktop app

Frequently asked questions

How do I install the Sendmux Attachments Claude Code skill?

Install via the ClaudSkills desktop app (one click) or copy SKILL.md from the source repository to ~/.claude/skills/sendmux-attachments/SKILL.md and restart Claude Code. Both flows are detailed at claudskills.com/install/.

What does the Sendmux Attachments skill do?

Is this skill free to install?

Yes. ClaudSkills is an open registry — every skill keeps its source repository's license, and manual install via copy is free. ClaudSkills Pro ($9/mo, $79/yr, or $149 one-time) adds one-click install via the desktop app and a multi-signal Quality Score.

When should I use the Sendmux Attachments skill?

Use Sendmux Attachments when your Claude Code task falls under the Product category — specifically in the ux research area. Claude Code auto-discovers installed skills and invokes the right one based on the task description, so you can also ask Claude directly (e.g. "use Sendmux Attachments" or describe the task and let Claude pick). Browse related skills at /category/product/.

What is a Claude Code skill and how does the Sendmux Attachments skill fit in?

A Claude Code skill is a SKILL.md file that lives under ~/.claude/skills/<name>/ and tells the Claude Code CLI agent how to perform a specific task (instructions, prompts, allowed tools). Skills are auto-discovered at session start. Sendmux Attachments is one of 67,000+ skills indexed in the open ClaudSkills catalog, classified under the Product category. Learn more at /learn/what-is-a-claude-skill/.

Attribution & license

Source: https://github.com/Sendmux/skills/blob/HEAD/plugins/sendmux/skills/sendmux-attachments/SKILL.md
Author: Sendmux

Cite this skill

If you reference this skill in a blog post, paper, or documentation, you can cite it as:

APA

Sendmux. (2026). Sendmux Attachments [Claude Code skill]. ClaudSkills. https://claudskills.com/skills/sendmux-attachments/

BibTeX

@misc{sendmux-attachments-2026,
  author    = {Sendmux},
  title     = {Sendmux Attachments [Claude Code skill]},
  year      = {2026},
  publisher = {ClaudSkills},
  url       = {https://claudskills.com/skills/sendmux-attachments/}
}

Embed this skill

Promote, attribute, or link this skill from your own README, blog post, or documentation. All three snippets are free to use — no sign-up, no API key. More distribution surfaces →

Badge

[![ClaudSkills](https://claudskills.com/badge/sendmux-attachments.svg)](https://claudskills.com/skills/sendmux-attachments/?utm_source=badge&utm_medium=readme&utm_campaign=skill_badge)

Security scan

Grade A · scanned 2026-07-11 — free static scan against the OWASP Agentic Skills Top 10.

No risk patterns were found in any of the ten OWASP-aligned categories. How grading works ›

✓ Prompt injection
✓ Data exfiltration
✓ Supply chain
✓ Reverse shell
✓ Credentials
✓ Execution
✓ Filesystem
✓ Persistence
✓ Obfuscation
✓ Network

Show this grade on your repo (click to copy):

[![Security: A](https://img.shields.io/badge/Security-A-2e7d32)](https://claudskills.com/skills/sendmux-attachments/#security)

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Browse all Product skills → Top 100 skills

Part of ClaudSkills — the open registry for Claude Skills & Claude Code Skills. · What's New · Install guide · About · llms.txt

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