What is DNS?
DNS connects a domain name, such as example.com, to the servers and services that run the website, email, and other internet services for that domain.
Domain Diagnostic Tool
DNS & Domain Health Checker
Check your domain, DNS records, website status, SSL certificate, email setup, SPF, DMARC, and common configuration issues in one place.
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Domain Health Summary
Health report
Enter a public domain to check DNS, website status, SSL, email DNS, redirects, and common configuration issues.
Turn a warning into a useful next check
If DNS resolves but the website returns 403, compare the page in your browser and check the hosting firewall or CDN logs. The server may be blocking automated requests; that result alone does not prove the website is down for visitors. A timeout is similarly inconclusive until you compare another connection and the provider’s status page.
After a DNS change, compare the exact hostname and record type with your DNS host’s authoritative records. Cached answers can differ until their TTL expires. This tool queries from Port233’s server, so it cannot confirm worldwide propagation. Undetected records may also reflect resolver failures. Save the report and confirm the discrepancy before replacing a working record.
DNS, email, SSL, and domain health basics
What are A and AAAA records?
A records point a domain to an IPv4 address. AAAA records point a domain to an IPv6 address. These records help browsers find the server hosting your website.
What are MX records?
MX records tell other mail servers where to deliver email for your domain. If a domain has no MX records, it may not be able to receive email.
What is an SPF record?
SPF is an email security record that lists which servers are allowed to send email for your domain. It helps reduce spoofing and fake email.
What is a DMARC record?
DMARC tells receiving mail servers what to do when an email fails SPF or DKIM checks. It can be used to monitor, quarantine, or reject suspicious email.
What is DKIM?
DKIM adds a digital signature to outgoing email. It helps receiving mail servers verify that the email was genuinely sent by an authorised system and was not changed in transit.
What is an SSL certificate?
An SSL certificate allows a website to use HTTPS. It helps encrypt traffic between the visitor and the website and proves that the certificate was issued for the domain.
Why does HTTP to HTTPS redirect matter?
If HTTP does not redirect to HTTPS, visitors may access an insecure version of the website. Redirecting to HTTPS helps protect users and improves trust.
What is a domain health check?
A domain health check reviews the main technical settings that keep a domain, website, and email working properly. This includes DNS, SSL, redirects, and email security records.
Need help fixing your domain, website, or business email?
Port233 helps small businesses configure DNS, websites, SSL certificates, Microsoft 365, Google Workspace, email security records, and reliable online infrastructure.
Port233 Toolkit
Managing DNS, domains, or email setup?
Use the Cyber Essentials resource and IT Consultant Bundle Pack to document DNS records, domain ownership, email security, SPF/DKIM/DMARC checks, renewals, and client handover notes.
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Useful external services
Recommended external tools
If your DNS or domain setup needs fixing, you may need a reliable domain registrar, DNS provider, email host, or privacy-focused business suite.
Proton Mail
Useful for encrypted email, custom-domain mail, email aliases, and privacy-focused business communication.
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