“The remote server returned an error: (308) Permanent Redirect” – what it means

Verdict: Not a site problem. Your site correctly redirects http:// to https:// with a 308. The checker's HTTP client doesn't follow 308, so it reports an error. Google treats 308 like 301. To clear the warning, make the redirect a 301.

What the warning checks

Web servers such as Caddy and Vercel use 308 (permanent, method kept) for the HTTP→HTTPS redirect.

Does it hurt email delivery?

• Google's documentation groups 301 and 308 together as permanent redirects: no SEO impact.
• Email delivery is not affected at all.

What to do

1. Optional: switch the HTTP→HTTPS redirect to 301. Caddy: redir https://example.com{uri} 301 in an http:// site block. Nginx: return 301 https://$host$request_uri;.
2. Re-run the report to confirm.

Check what actually matters

SPF, DKIM and DMARC decide whether Gmail, Outlook and Yahoo accept your mail.

After the fix, send a test email to see SPF, DKIM and DMARC pass on a real message, then keep an eye on it: free DMARC monitoring shows every service that sends mail as your domain and which ones fail, in plain English.

Sources

• Google Search Central: redirects
• Caddy: redir directive

Other warnings explained

• SOA Serial Number Format is Invalid
• SOA Expire Value out of recommended range
• Blacklisted by SEM FRESH
• Blacklisted by SEM URIRED
• [SUPPLEMENTAL] Brand Logo not appearing in inboxes
• Listed by CSS (Spamhaus ZEN 127.0.0.3)
• Listed on UCEPROTECT Level 3