emailguard

Fast, practical heuristics for validating business email domains during signup.

emailguard filters out disposable, masked, or misconfigured email domains using lightweight DNS inspection and a curated blocklist of known temporary email providers.
It’s designed for B2B SaaS signup flows where you want real business emails, not throwaway addresses.

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⚡ Features

• ✅ Checks MX records (fast, 1s timeout)
• ✅ Blocks disposable & temp-mail domains (auto-syncs from GitHub)
• ✅ Detects masking/aliasing services via MX heuristics
• ✅ Caches verdicts and DNS results in memory
• ✅ Safe defaults for consumer providers (Gmail, Outlook, etc.)
• ✅ Zero external services — pure Go + DNS

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🚀 Installation

go get github.com/vandit1604/emailguard

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🧠 Example

package main

import (
    "fmt"
    "github.com/vandit1604/emailguard"
)

func main() {
    ok := emailguard.IsLegitEmail("user@company.com")
    if !ok {
        fmt.Println("Reject: unverified or disposable domain")
    } else {
        fmt.Println("Looks good ✅")
    }
}

Output:

Looks good ✅

or, for a disposable domain:

Reject: unverified or disposable domain

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🧩 How it works

1. Clones disposable-email-domains into /tmp (once per process).

2. Checks:

   • Is domain in blocklist?
   • Has valid MX?
   • Does MX contain masking keywords? (mask, relay, forward, tempmail, etc.)
   • Are MX registrable domains disposable?

3. Caches DNS + verdicts for 5 minutes.

4. Returns a simple boolean — fast, deterministic, low overhead.

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⚙️ Config / Policy

Modify allowlist, mxBadKeywords, or cache TTLs inside the package if needed.

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📦 Use cases

• Block signups using temp or masked emails
• Improve lead quality in B2B products
• Sanitize marketing imports
• Gate API access behind legit company addresses

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🧑‍💻 License

MIT — free for commercial use. Attribution appreciated but not required.