66 lines
2.1 KiB
Markdown
66 lines
2.1 KiB
Markdown
# SMTP SPF/DKIM Bounce Recovery
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**Context:** July 11, 2026 — Apex Track Experience confirmation emails to 2 Gmail recipients bounced with `550-5.7.26 Your email has been blocked because the sender is unauthenticated`.
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## Root Cause
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The WP Mail SMTP plugin sends through SiteGround's SMTP relay (`c1113726.sgvps.net:2525`), but the SPF record for `apextrackexperience.com` didn't cover all outbound IPs that SiteGround routes through.
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The bounce showed the connecting IP as `136.175.108.114` (MXroute LLC), NOT the expected SiteGround IP (`35.212.86.161`). Two different outbound paths were being used and only one was in SPF.
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## Diagnosis
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1. Check the current SPF record:
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```bash
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dig +short TXT <domain>
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```
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2. Check what IP the SMTP relay resolves to:
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```bash
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dig +short <smtp-host>
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```
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3. Cross-reference with SPF include chains:
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```bash
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# Follow includes recursively
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dig +short TXT <include-domain>
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```
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4. Check DKIM:
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```bash
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dig +short TXT default._domainkey.<domain>
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```
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5. Check DMARC policy:
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```bash
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dig +short TXT _dmarc.<domain>
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```
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## Fix
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1. Add the SMTP relay IP to the SPF record:
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```
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v=spf1 +a +mx ip4:<SMTP-IP> include:<autogen-include> ~all
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```
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2. Ensure DKIM is published (usually auto-generated by the email provider)
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3. Set DMARC to `p=none` initially (monitor), then `p=quarantine` after verification
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4. After SPF fix, **resend the failed emails manually** — SPF only blocks, it doesn't queue and retry. Gmail doesn't auto-retry SPF failures.
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## Re-sending After Fix
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For WPForms confirmation emails that bounced:
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- SMTP: c1113726.sgvps.net:2525 TLS
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- User: contact@apextrackexperience.com
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- Build the email manually as HTML with the same format as the WPForms notification
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- Send via smtplib through the same SMTP relay
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- Include full registration details (driver, passenger, vehicle, package, amount, waiver status)
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## Prevention
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- Enable **WP Mail SMTP email logging** (`wp_mail_smtp` option in wp_options) — without logging, there's no delivery trail
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- Add **all** outbound relay IPs to SPF — SiteGround may route through multiple IPs
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- Test with a throwaway Gmail address after SPF changes
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