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The WordPress Email Authority

WordPress email errors are frustrating because the message usually tells you what went wrong, not why or what to do about it. This tool translates common SMTP error codes, bounce strings, and wp_mail_failed output into plain-English causes and fixes.

SMTP Error Decoder

Paste a bounce message, SMTP error code, or wp_mail_failed output below. Get the cause, who’s at fault, and the fix.

What this tool covers

The decoder recognises the most common WordPress email failure patterns:

  • Authentication errors — wrong credentials, SMTP AUTH disabled, App Password issues
  • Microsoft 365 errors — 550 5.7.515 (SMTP AUTH off), 550 5.7.30 (relay not permitted), 550 5.7.350 (policy block)
  • SPF and DMARC rejections — including Gmail’s 550 5.7.26
  • Connection failures — host unreachable, port blocked, TLS handshake errors
  • Bounce codes — bad address (5.1.1), mailbox full (452), rate limiting (421)
  • DKIM failures — key mismatch, missing signature, propagation lag
  • WordPress-specific — wp_mail_failed hook output, PHPMailer error strings

Each result includes a fault attribution — whether the problem is yours to fix, the recipient server’s issue, or a relay problem — so you know where to direct troubleshooting effort.

How to get the error string

WP Mail SMTP: Settings → Email Log → click a failed message → copy the full error from the Error detail panel.

FluentSMTP: Dashboard → Email Logs → failed row → Error column.

PHP error log: Search for wp_mail_failed or SMTP ERROR in wp-content/debug.log.

Bounce email: Forward the bounce notification to yourself and paste the diagnostic block (the indented lines beginning with the SMTP code).

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