List every hostname that needs coverage and verify its A and any AAAA records. Confirm the web virtual host and challenge path are reachable. Review CAA records and whether DNS validation is available through the DNS management supported by your installation.

1. Select the domain and open Manage Virtual Server > Setup SSL Certificate. Choose the SSL Providers tab.
2. Review the requested names and remove accidental or unreachable aliases. Select a supported provider; provider choices beyond Let's Encrypt depend on the Virtualmin edition.
3. Enable automatic renewal and the preliminary connectivity check. Choose wildcard coverage only when the installation can complete the necessary DNS validation for the zone.
4. Request the certificate and read the result. Correct a failed validation before repeated attempts rather than consuming certificate-authority rate limits.
5. Inspect the installed certificate, then visit the HTTPS site and test application URLs. Configure an HTTP-to-HTTPS redirect only after the HTTPS endpoint works correctly.
6. Monitor expiry and renewal logs. Keep validation functional when moving DNS, adding a proxy or changing the document root.

Modern hostname-based TLS normally uses SNI on a shared address. The certificate must still cover the requested name and the web server must select the correct virtual host.

Test the public hostname from outside the server and inspect the certificate names, chain and expiry. Check aliases and IPv6 separately. Verify that the application does not create a redirect loop or load sensitive content over HTTP.

For failure, distinguish DNS mismatch, inaccessible challenge, CAA restrictions and unsupported validation mode. A website certificate does not automatically prove the panel or mail listener uses the same certificate. Keep a valid previous certificate while correcting a replacement failure.

• Making a Virtualmin BIND zone authoritative
• Changing a Virtualmin server hostname safely
• Fixing a Virtualmin domain that shows the wrong website
• Changing PHP limits for one Virtualmin website

• Virtualmin: How To Add An SSL Certificate
• Virtualmin: Generate Letsencrypt Cert
• Let's Encrypt: Challenge Types