Paste your email draft below and Smart Email Guard checks for missing attachments, links, and CCs before you hit Send — in your browser, no sign-up, no install needed.
Also works as a Chrome extension in Gmail, Outlook, and Yahoo Mail.
You hit Send, and half a second later your stomach drops. These are real stories from real people.
"I just sent another email — and forgot to include the attachments. How do you all avoid this mistake?"
Actuaries — highly analytical professionals — have developed 6-step manual rituals because built-in detection "never prompts" them. Source: Reddit
"I can't even say how many times I have forgotten attachments and had to send a follow-up email."
A Fastmail user's delight at discovering attachment detection got 33 comments debating which email clients have it — and which don't. The confusion IS the market gap. Source: HN
"I forgot to attach the file to the email I sent and now I have to send an awkward second email."
150+ upvotes for a one-sentence complaint. One commenter did it "on purpose" — then forgot the attachment on the second email too. The pain is universal. Source: Reddit
This is exactly what the extension does — type an email below, toggle which checks to run, and hit Send.
No email is actually sent — this is just a demo. Your text stays in your browser.
Three steps. No configuration. Your email client stays exactly the same.
Download from GitHub Releases. Unzip, load in chrome://extensions. No account, no sign-up, no permissions beyond your email tabs.
Smart Email Guard quietly monitors Gmail, Outlook, and Yahoo Mail. It reads the text you type in real time — nothing else.
If you mention an attachment, link, or CC but forget to include it, a gentle warning pops up. Fix it and send. That's it.
No store needed — sideload in 5 steps. Works on Chrome, Edge, Brave, and any Chromium browser.
Get the latest release from GitHub
smart-email-guard-v1.0.1.zipExtract anywhere on your computer — Desktop, Documents, wherever you keep extensions.
Go to Extensions in your browser
chrome://extensionsToggle the switch in the top-right corner of the extensions page.
Click "Load unpacked", select the folder. Smart Email Guard is now active!
Detailed instructions in INSTALL.md · Zero sign-up · 100% local · Works offline
Smart Email Guard works right inside Gmail, Outlook, and Yahoo. Five real scenarios — all caught before you hit Send.
Detects 10+ phrases like "I've attached", "see attached", "enclosed"
Catches "link below", "see URL", "click here" with no actual link
Warns if you promise to CC someone but they aren't in the CC field
Click the extension icon to see what passed and what needs attention
When everything's fine, you won't even notice it's there
These are real screenshots from the Chrome extension — identical to what you'll see on install.
Download v1.0.1 (Free) →
Built-in detection is inconsistent and keyword-only. Other extensions tackle one problem at most. Smart Email Guard checks everything — all at once.
| Feature | Smart Email Guard | Gmail Built-in | Mail Attach | Boomerang |
|---|---|---|---|---|
| Missing attachment detection | ✓ | ✓ (inconsistent) | ✓ | ✕ |
| Missing link detection | ✓ | ✕ | ✕ | ✕ |
| Missing CC recipient check | ✓ | ✕ | ✕ | ✕ |
| Works in Outlook & Yahoo Mail | ✓ | ✕ (Gmail only) | ✕ (Gmail only) | ✕ (Gmail only) |
| Custom pattern rules | ✓ | ✕ | ✕ | ✕ |
| 100% local, no data leaves browser | ✓ | ✓ | ✕ (reads email) | ✕ (cloud-based) |
| Price | Free | Free | ? (commercial) | $5–$50/mo |
Sources: Gmail inconsistency confirmed by HN users · Mail Attach analyzed at mailattach.co · Boomerang pricing from boomeranggmail.com
Short answers. No marketing spin.
No. Everything happens inside your browser. Smart Email Guard watches the text you type in your compose window — it never reads received emails, never accesses your inbox, and never sends data to any server. There is no backend. The extension is 100% self-contained.
Gmail only catches missing attachments — and even then, inconsistently. HN users report it works on some accounts but not others, and toggling experimental features randomly fixes or breaks it. It doesn't detect missing links, forgotten CCs, or work in Outlook/Yahoo. Smart Email Guard catches all three mistakes, works across all major email clients, and never fails silently.
Gmail, Outlook Web (outlook.live.com and outlook.office.com), and Yahoo Mail. Basically any web-based email client. It works by monitoring the compose window DOM, so it's platform-agnostic as long as you're using the web version.
The extension is fully functional and free — including unlimited custom patterns. The Supporter tier ($3.99/mo or $29 lifetime) is for people who want to fund Pro development (regex, multi-language, cloud sync) and get early access when those features ship. Think of it as a Patreon, not an upgrade. No feature gating. No data collection. No upsells.
The extension is fully functional. Pay to support Pro development.
Not speculation — real demand signals from real communities.
Top comment (31 upvotes): a 6-step manual ritual. Outlook's built-in detection "literally never prompted me."
View thread →Sales professionals coping with email mistakes through dark humor. Forgetting attachments costs deals.
View thread →"Embarrassing emails to the wrong recipient" — hundreds of stories, zero tool recommendations.
View thread →A developer posted Attachment Reminder in May 2026 — instant traction. The demand is proven.
View subreddit →A simple attachment reminder generated 37 points and 33 comments on Hacker News. People love this feature.
View thread →7.2M subscriber subreddit: someone self-describes as embarrassed about sending emails without attachments.
View thread →Full market evidence report: ledger/market-evidence-email-oops-detection.md — 10 pain quotes, 12 competitors analyzed, willingness-to-pay evidence from Boomerang ($5–$50/mo) and Grammarly ($30/mo)
Comparisons, reviews, and permanent fixes — articles from our blog.