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Accessing webmail through SquirrelMail, Horde, or Roundcube should normally work without issues. However, administrators may sometimes encounter a blank screen or repeated login failed errors even when the username and password are correct.

This issue is usually caused by incorrect domain ownership, corrupted user domain files, or a hostname conflict within the cPanel server.

This guide explains how to troubleshoot and resolve the problem step by step.

Issue Description

While accessing webmail clients such as:

• SquirrelMail
• Horde
• Roundcube

you may notice:

• Blank webmail page after login
• Login failure errors for all mail clients
• Authentication failure despite correct credentials

These symptoms typically indicate a domain ownership mismatch on the server.

Solution Steps

Step 1: Check Domain Ownership

Login to your server via SSH as root and run:

/scripts/whoowns domain.com

Replace domain.com with the affected domain name.

The command should display the correct cPanel username owning the domain.

Step 2: Rebuild Domain Ownership Files

If no ownership is shown, rebuild the user domain configuration files.

Navigate to /etc directory:

cd /etc

Move existing domain mapping files:

mv userdomains userdomains.bak
mv domainusers domainusers.bak
mv trueuserdomains trueuserdomains.bak

Now rebuild ownership data:

/scripts/updateuserdomains
/scripts/whoowns domain.com

Recheck whether the domain ownership appears correctly.

Step 3: Fix Incorrect Domain Ownership

If the domain shows the wrong owner:

1. Open the incorrect user file:

/var/cpanel/users/username

2. Remove the DNS entry associated with the affected domain.
3. Save the file.
4. Run again:

/scripts/updateuserdomains

This refreshes the domain ownership configuration.

Step 4: Resolve Hostname Conflict

If you receive the following error:

Unable to read /etc/trueuserdomains
Serious Problem — This should never happen!!
The hostname (domain.tld) is owned by the user <username>

This indicates a hostname conflict.

The server hostname is set to the same domain as the cPanel account, which causes ownership conflicts.

Fix Hostname Conflict

1. Login to WHM.
2. Navigate to:

WHM → Networking Setup → Change Hostname

3. Change the hostname:

domain.tld – no
server.domain.tld – yes

The hostname should always be a subdomain, not the main domain.

Step 5: Rebuild Domain Files Again

After updating the hostname, repeat:

cd /etc
mv userdomains userdomains.bak
mv domainusers domainusers.bak
mv trueuserdomains trueuserdomains.bak
/scripts/updateuserdomains

Domain ownership should now be correctly assigned, and webmail access will function normally.

Conclusion

Webmail blank pages or login failures in SquirrelMail, Horde, and Roundcube are commonly caused by domain ownership inconsistencies or hostname conflicts. Rebuilding domain configuration files and correcting the server hostname typically resolves the issue quickly.

If you require help, contact SupportPRO Server Admin