Introduction

In email marketing and communications, bounce rates exceeding ~5% usually push campaigns into spam folders and damage domain reputation. Most list-cleaning tools return scores without evidence. This plugin lets agents autonomously run checks before sending—every decision is traceable to the actual DNS queries made during that run; probe failures are honestly recorded as unverified, never guessed.

Plugin Purpose

This is a network-enabled tool plugin maintained by ChenneyZhuang. It determines the deliverability of an address before sending email through four sequential DNS gates, avoiding the reputation loss caused by bounces.

Core Features

  • Four sequential DNS gates: check address format, dead domains (A/NS), MX records, and role/placeholder patterns in order.
  • Batch processing: supports CSV input and output, with output lines mapped 1:1 to input lines.
  • Traceability: every decision result can be traced back to actual DNS queries that occurred during execution.
  • Integrity rule: never fabricates a pass.
  • Cross-platform support: supports Claude Code, DSH, Hermes, and Codex.

Installation and Activation

Dependencies: Running requires dig or a Python DNS resolution library.

Clone into the skills directory for Claude Code:

git clone https://github.com/ChenneyZhuang/email-deliverability-audit ~/.claude/skills/email-deliverability-audit

How It Works

The plugin evaluates email addresses through four gates:

  1. Gate 1: Format check: validates whether the address format is correct.
  2. Gate 2: Dead-domain check: determines whether the domain is a dead domain (via A/NS records).
  3. Gate 3: MX check: confirms whether the domain has mail exchange records.
  4. Gate 4: Role and placeholder check: flags role accounts (such as info@) or local parts consisting only of digits.

Based on the decision result:
* sendable: passed all four gates.
* risky: passed the first three gates but failed at Gate 4 (role account or placeholder).
* dead: failed in one of the first three gates.

Typical Usage

  • Audit name@gmail.com, resulting in sendable.
  • Audit bad@@example.com, resulting in dead (Gate 1 format error).
  • Audit site@australia.gov.au, resulting in dead (Gate 3 no MX).

Use Cases and Notes

  • Use case: Suitable for batch cleaning and validation of target addresses before sending email, preventing bounces and domain reputation decline caused by invalid addresses.
  • Note 1: Gate 4 marks role accounts as risky rather than dead. The delivery success rate of role accounts depends on the recipient’s filtering policy.
  • Note 2: Proving that a domain is deliverable via the audit does not prove that the specific mailbox address exists (no SMTP RCPT probe).
  • Note 3: The plugin runs with the permissions of the current DSH process. Before installation, the source code and license (MIT) should be reviewed.

Conclusion

With this mechanism, agents can objectively verify the validity of addresses before sending email. For more information, refer to the GitHub repository or the DSH plugin directory.