When a JSP site stops loading, shows intermittent errors, or works from one browser but not another, the cause is often not the JSP code itself. In many hosting cases, DNS records, mail routing, SSL configuration, or domain-level settings are the real reason the application cannot be reached correctly. For Java hosting, Tomcat hosting, and JSP hosting in a control panel such as Plesk, it is important to check the surrounding services first, especially when the site depends on a domain, a mail-enabled account, or a secure HTTPS setup.
This guide explains how to identify DNS and mail-related problems that can look like JSP hosting issues, how to test them, and how to separate application errors from domain configuration problems. It also includes practical checks for My App Server, Apache Tomcat, and private JVM setups in a shared hosting account.
What DNS and mail settings can affect in JSP hosting
JSP applications usually run behind a web server such as Apache and a servlet container such as Tomcat. If the domain does not resolve correctly, points to the wrong IP address, or has incomplete DNS records, users may never reach the application. In some cases, a mail misconfiguration can also create the impression that the JSP site is broken, especially if password reset emails, order confirmations, or contact forms are not delivered.
Common symptoms include:
- The website does not open for some users, but works for others.
- The browser shows a DNS-related error instead of your JSP page.
- HTTPS redirects fail or produce certificate warnings.
- Forms submit successfully, but no email is received.
- Password recovery or account activation emails are missing.
- The application works by server IP or temporary URL, but not by domain name.
- Mail-related failures appear in the application logs even though the JSP code is correct.
In a managed hosting environment, the goal is to confirm whether the issue is inside the application layer, the Tomcat service, or the domain/mail layer. That saves time and prevents unnecessary changes to working JSP code.
First checks when a JSP site looks broken
Confirm whether the problem is global or local
Start by testing the site from more than one network and more than one device. If the site fails only on one internet connection, the issue may be DNS caching on the client side or a local resolver problem. If it fails everywhere, the domain or hosting configuration is more likely.
Useful checks:
- Open the site in an incognito/private browser window.
- Test from a mobile connection as well as office or home internet.
- Try resolving the domain from a different DNS provider.
- Check whether the same issue happens with www and non-www versions.
Check whether Tomcat is actually running
In a JSP hosting setup, a domain can be correctly configured while the Java application service is stopped. With My App Server in Plesk, verify that the private JVM or Tomcat instance is running and bound to the expected service settings. If Tomcat is down, the website may return connection errors, gateway errors, or blank pages depending on the Apache integration.
If the service is running but the site still fails, continue with DNS and mail checks before changing application code.
How to check DNS problems that affect JSP hosting
DNS controls where the browser sends traffic for your domain. If the A record, AAAA record, CNAME, or nameserver setup is wrong, users may be directed to the wrong server or receive no answer at all. This is one of the most common reasons a JSP site appears unstable after migration, domain renewal, SSL installation, or nameserver changes.
Verify the A record and AAAA record
The A record should point to the correct IPv4 address for the hosting account. If your service uses IPv6, the AAAA record must also be correct. A stale AAAA record is a frequent cause of intermittent failures, because some networks prefer IPv6 and others prefer IPv4.
What to check:
- Does the domain resolve to the current hosting IP?
- Is there an old A record left from a previous provider?
- Is there an AAAA record that points to an unused or wrong IPv6 address?
- Do both www and the root domain resolve correctly?
If the website works with one hostname but not another, compare the DNS records carefully. For JSP applications behind Apache and Tomcat, all intended hostnames should point to the same valid hosting target unless you deliberately split them.
Check nameserver delegation
If the domain was recently transferred, renewed, or moved to a new DNS service, verify that the registrar still points to the correct nameservers. Incorrect nameserver delegation can cause the hosting account DNS zone to be ignored entirely.
Signs of a nameserver issue:
- The domain shows old records even after changes in the control panel.
- Different DNS tools return different answers.
- Some records appear missing from public lookups.
- Mail and website changes do not take effect.
In Plesk, make sure the domain’s DNS zone is active if you intend to manage records there. If DNS is hosted elsewhere, confirm that the external DNS zone matches the expected web and mail setup.
Look for propagation delays and caching
After a DNS update, some users may still reach the old destination until caches expire. This is normal, but it can look like an unstable JSP host if the timing is not understood. Check the TTL values in the zone and remember that local resolvers, browsers, routers, and ISP caches may all store previous values.
Practical step: test the domain using a public DNS resolver and compare it with the result from your local machine. If the public answer is correct but your machine still shows the old IP, clear the local DNS cache or wait for the TTL to expire.
Check for conflicting CNAME, MX, and web records
Misconfigured DNS zones sometimes contain records that conflict with the site setup. For example, a CNAME record on the root domain, an incorrect wildcard record, or a duplicate host record can cause unpredictable behavior. While this may not directly break JSP code, it can stop the browser from reaching the correct Apache and Tomcat endpoint.
Review the zone for:
- Duplicate A or AAAA records for the same hostname.
- Incorrect CNAME usage on the root domain.
- Old verification records from previous services.
- Wildcard records that intercept the intended hostnames.
How SSL issues can look like JSP or DNS failures
SSL and DNS often interact. A valid DNS record is needed for certificate issuance and renewal, and an incorrect certificate can make a working JSP application seem unavailable. In a hosting platform, HTTPS problems may appear as browser blocks, redirect loops, or blank pages after migrating a site or enabling a new domain.
Confirm that the certificate matches the hostname
If the certificate was issued for www.example.co.uk but users visit example.co.uk, the browser may warn about the certificate name mismatch. The same applies if the domain changed recently and the certificate was not reissued.
Check whether the certificate covers:
- The root domain.
- The www subdomain.
- Any additional hostnames used by the JSP application.
Check HTTPS redirects and mixed content
Some JSP applications redirect all traffic to HTTPS at the application or Apache level. If the redirect points to the wrong hostname or creates a loop, the site may never load properly. Also check whether the application loads insecure external resources, because mixed content warnings can hide parts of the page.
Useful tests:
- Open the site with both http:// and https://.
- Check whether the redirect lands on the expected hostname.
- Verify whether the certificate is installed for the exact domain being used.
- Inspect the browser console for blocked resources.
Reissue the certificate after DNS changes if needed
If the domain’s DNS was changed recently, certificate validation can fail until the DNS records are correct. For HTTP-01 or similar validation methods, the public DNS response must point to the correct server. If validation cannot reach the site, renewal may fail and the browser may show security errors.
How mail settings affect JSP applications
Many JSP sites use email for contact forms, account creation, login confirmation, ticket systems, and password resets. If mail is misconfigured, the application may still load, but it will feel broken to users because key workflows do not complete.
Check MX records and mail routing
MX records tell the internet where to deliver mail for your domain. If they are wrong, message delivery may fail or go to the wrong host. In a hosting control panel, the domain may be set to local mail handling or remote mail handling depending on where mailboxes are hosted.
Verify:
- The MX records point to the intended mail service.
- The priority values are correct.
- There are no old MX records from a previous provider.
- The mail handling mode matches your actual setup.
Check SPF, DKIM, and DMARC
Even when mail leaves the application successfully, receiving servers may reject or quarantine it if sender authentication is incomplete. That can cause apparent JSP errors when the real issue is email deliverability.
Review these records:
- SPF should authorize the server or service sending the mail.
- DKIM should sign outgoing messages if available.
- DMARC should be aligned with your sending policy.
If your JSP app sends via SMTP, make sure the sending host, username, and envelope-from address all match the domain policy. If the app sends directly through the server, the host may require proper mail routing and authentication settings.
Test contact forms and transactional mail
A working site can still fail if the form handler or mail transport is blocked. Use a simple test submission and check the following:
- Did the JSP application return success?
- Is the message present in the mail logs?
- Was it accepted by the local mail system or SMTP relay?
- Did the recipient’s mailbox receive it?
If the form submits but no mail arrives, the issue may be in DNS mail settings, SMTP credentials, anti-spam policies, or the server’s outbound mail limits rather than in the JSP code itself.
Practical checks in Plesk and My App Server
When using My App Server in Plesk, you can separate application-level problems from domain-level problems more efficiently. This is useful for JSP hosting, servlet hosting, and private JVM hosting in a shared environment.
Check the domain assignment
Make sure the domain is assigned to the correct subscription and the correct application instance. If the site is deployed to the wrong document root or Tomcat context path, DNS may be correct but the browser will still show the wrong content or an error page.
Review the Apache and Tomcat connection path
Many JSP setups use Apache as the front end and Tomcat as the application engine. If Apache is pointing to the wrong backend port or if the service connector is misconfigured, users may receive gateway errors that resemble DNS problems.
Check that:
- Tomcat is running.
- The application context is deployed correctly.
- The Apache virtual host points to the intended domain.
- SSL is configured consistently on both layers.
Confirm the selected Java version
If a site loads by IP but fails after routing through the domain, the cause may still be a Java runtime mismatch. Some JSP applications require a specific Java version, and an incorrect JVM may trigger startup failures, application exceptions, or blank pages.
Use the Java management options in My App Server to confirm that the selected runtime matches the application’s requirements.
A step-by-step troubleshooting workflow
Use the following order to identify whether the problem is DNS, SSL, mail, or the JSP application itself:
- Test the domain from more than one device and network.
- Check whether the site resolves to the correct IP address.
- Verify that the domain uses the correct nameservers.
- Inspect A, AAAA, CNAME, and www records for conflicts.
- Confirm that Tomcat and My App Server are running.
- Check whether HTTPS works without certificate errors.
- Review MX, SPF, DKIM, and DMARC records if email is involved.
- Test the mail flow used by forms, registration, or password reset.
- Compare browser errors with server logs in Plesk.
- Only then move to JSP code or application deployment issues.
Examples of common failure patterns
Example 1: Site works by IP but not by domain
This usually points to DNS, not JSP. The domain may be resolving to the wrong server, or the web host may not yet have the correct virtual host configuration. Check the A record, nameservers, and Apache domain mapping.
Example 2: HTTPS shows a certificate warning after a migration
The domain likely points correctly, but the SSL certificate was not reissued for the current hostname or the DNS validation record is wrong. Confirm certificate coverage and test both root and www hostnames.
Example 3: Contact forms submit but no emails arrive
The application may be processing correctly, while mail routing or authentication is failing. Review MX, SPF, DKIM, and whether the server is allowed to send for the domain. Also check spam and quarantine folders.
Example 4: Some users see the site, others get an error
This often indicates DNS propagation, cached records, or an incorrect AAAA record. Compare lookups from different networks and remove obsolete records if needed.
What to collect before contacting support
If you need help from your hosting provider, sending complete diagnostics will shorten resolution time. Include:
- The domain name and affected hostname.
- The exact error message from the browser.
- The time when the issue started.
- Whether HTTP, HTTPS, or email is affected.
- Results from a DNS lookup for A, AAAA, MX, and nameserver records.
- Whether Tomcat or My App Server shows any service errors.
- Relevant log lines from Apache, Tomcat, or mail logs.
For JSP hosting cases, it also helps to note the application version, Java version, and whether the issue started after a deploy, certificate change, or DNS update.
FAQ
How do I know if the problem is DNS or Tomcat?
If the domain does not resolve, resolves to the wrong IP, or works only in some locations, it is likely DNS. If the domain resolves correctly but the application gives a gateway error, blank page, or startup failure, check Tomcat, the Java version, and the app deployment.
Can a mail setting break my JSP website?
It usually does not break page loading, but it can break important functions such as contact forms, registration emails, password resets, and order notifications. That often makes the site seem broken even when the web layer is working.
Why does the site work on one browser but not another?
One browser may be using cached DNS data or cached HTTPS information. Test in a private window and compare results from another network. If the issue is still present, inspect DNS records and SSL settings.
Do I need to change my JSP code if the DNS record is wrong?
No. DNS problems are usually fixed in the domain or control panel settings, not in the JSP application. Only change code if logs show a true application error after DNS, SSL, and mail checks are complete.
Can My App Server help with these checks?
Yes. My App Server in Plesk lets you control the Java service, choose a suitable Java version, and manage Tomcat deployments in one place. That makes it easier to confirm whether the issue is in the application runtime or in the surrounding domain services.
Conclusion
When a JSP site fails, the root cause is often outside the JSP code. DNS records, nameserver delegation, SSL certificates, and mail settings can all create symptoms that look like application failures. By checking domain resolution, HTTPS behavior, and mail routing before changing the application, you can quickly isolate the real problem and avoid unnecessary downtime.
In a hosting environment with Plesk and My App Server, the best approach is to verify the domain configuration, confirm that Tomcat and the private JVM are running, and then review SSL and mail records. This workflow is especially effective for JSP hosting, servlet hosting, and small to medium Java applications that depend on accurate DNS and reliable mail delivery.