If you arrived here looking for Pitney Bowes or Hasler mailing machine supplies (a common confusion with "HMC" standing for Heavy Mail Capacity or similar):
HMC Mail Checker 22 is a powerful and efficient desktop utility designed to verify the validity and deliverability of email addresses. Whether you manage marketing lists, clean up CRM data, or prevent high bounce rates, this tool helps you identify risky or invalid email addresses before they cause harm to your sender reputation.
When you run hmc-mail-checker22, you will see exit codes and status messages. Here is a quick reference:
| Code | Message | Meaning | Action |
| :--- | :--- | :--- | :--- |
| 0 | SUCCESS: Delivery confirmed | Test passed | None needed |
| 2 | WARN: Deferred (4xx) | Remote server temporarily unavailable | Check remote MX logs |
| 5 | ERROR: Authentication failed (535) | Bad password or broken SASL | Reset password; check /etc/sasl2/hmc.conf |
| 10 | CRIT: HMC queue lock detected | Stale lock file in /var/lock/hmc/ | Run hmc-mail-checker22 --clear-locks |
| 14 | DKIM signature invalid | DNS record mismatch or body modified | Re-sign with correct selector |
| Tool | Scope | Auth | Batch support | |------|-------|------|----------------| | Gmail web interface | Full email | OAuth2 | No | | Google Admin Toolbox | MX/SPF/DKIM checks | None | No | | HMC Mail Checker 22 | Address validity + mailbox status | OAuth2 / IMAP | Yes |
For a global view of the queue:
hmc-mail-checker22 --queue-scan --status deferred
To view just messages for a specific domain:
hmc-mail-checker22 --queue-scan --domain contoso.com --verbose
If "22" refers to a specific release (e.g., HMC V9 R2.2 M.0 or similar), you may be looking for release notes regarding email functionality.
A critical feature for system admins is the tool's ability to check the IP address of the mail server against major RBLs (Real-time Blackhole Lists). If a server is listed, emails sent from it are likely to be marked as spam. HMC 22 provides immediate feedback on the reputation of the mail server in question.
