Roundcube error messages: complete troubleshooting guide

Roundcube is one of the most popular webmail applications used by Dutch hosting providers. While it usually works reliably, you may occasionally encounter error messages. In this guide, we cover the most common Roundcube errors and how to solve them.

1. Login failed

Symptom

You see the message "Login failed" when trying to log into Roundcube.

Cause

• Incorrect password or email address
• Account blocked due to too many login attempts
• IMAP server unavailable
• Password contains special characters

Solution

1. Check your credentials - Type your full email address (including @domain.com)
2. Reset your password - Do this via your hosting control panel (cPanel/DirectAdmin)
3. Wait 15-30 minutes - If blocked due to too many attempts
4. Avoid special characters - Use letters, numbers and basic punctuation in your password

Prevention

Store your password safely in a password manager and avoid multiple login attempts in succession.

2. Session expired

Symptom

While working, "Session expired" suddenly appears and you are logged out.

Cause

• Been inactive for too long
• Cookies blocked by your browser
• Multiple Roundcube tabs open
• Browser extensions deleting cookies

Solution

1. Log in again - This is the quickest solution
2. Check cookie settings - Allow cookies for your webmail domain
3. Temporarily disable adblockers - These can block session cookies
4. Use one tab - Close other Roundcube tabs

Prevention

Regularly save important emails as drafts and work in one browser tab.

3. Connection to storage server failed

Symptom

Error message "Connection to storage server failed" or "IMAP connection error".

Cause

• IMAP server temporarily unavailable
• Mail server maintenance
• Firewall blocking the connection
• DNS problems

Solution

1. Wait a few minutes - Often this is a temporary issue
2. Refresh the page - Press F5 or Ctrl+R
3. Try another browser - To rule out browser-specific issues
4. Check server status - Look at your hosting provider status page

Prevention

Keep your hosting provider email address handy for maintenance notifications.

4. Attachment too large

Symptom

When adding an attachment, "Attachment too large" or "File is too big" appears.

Cause

• File exceeds maximum upload size
• Total email size exceeds the limit
• PHP upload limit on server

Solution

1. Reduce file size - Compress images or create a ZIP file
2. Split large files - Send in multiple emails
3. Use a cloud service - Upload to Google Drive or WeTransfer and share the link
4. Contact hosting - Ask if the limit can be increased

Prevention

Keep in mind a maximum attachment size of 10-25 MB with most hosting providers.

5. Could not save message

Symptom

After clicking "Send", "Could not save message to Sent folder" appears.

Cause

• Mailbox quota reached
• Sent folder does not exist or is corrupted
• Incorrect permissions on IMAP folders

Solution

1. Clean your mailbox - Delete old emails from Sent and Trash
2. Empty the trash - This counts toward your quota
3. Check folder structure - Log in via cPanel/DirectAdmin and check folders
4. Recreate the Sent folder - Delete and let Roundcube create a new one

Prevention

Keep your mailbox under 80% of quota and clean up regularly.

6. Error loading message

Symptom

When opening an email, "Error loading message content" appears.

Cause

• Message is corrupted
• Connection problem during loading
• Message contains incompatible formatting

Solution

1. Refresh the page - Try opening the message again
2. View as plain text - Some HTML messages do not load properly
3. Download the message - Right-click on the message and choose "Download"
4. Open in an email client - Set up the account in Outlook or Thunderbird

Prevention

Keep your browser up to date and do not disable JavaScript.

7. Disk quota exceeded

Symptom

You cannot receive new emails and see "Disk quota exceeded" or "Mailbox is full".

Cause

• You have reached maximum storage space
• Large attachments in old emails
• Trash and spam not emptied

Solution

1. Sort by size - Delete the largest emails first
2. Empty Trash and Spam - These folders count toward quota
3. Remove old attachments - Download important attachments locally and delete emails
4. Upgrade your package - Ask your hosting provider for more space

Prevention

Set automatic deletion for spam and trash (e.g., after 30 days).

8. Unable to connect to server

Symptom

Roundcube will not load and shows "Unable to connect to server" or a blank page.

Cause

• Server offline or under maintenance
• DNS problems with your domain
• Unstable internet connection
• Expired SSL certificate

Solution

1. Check your internet - Open another website to test
2. Try direct IP - Ask your hosting provider for the direct IP address
3. Clear DNS cache - Open command prompt and type ipconfig /flushdns
4. Wait for maintenance - Check your provider status page

Prevention

Save your provider direct webmail address as backup.

General tips for Roundcube problems

• Keep your browser up to date - Old browsers can cause compatibility issues
• Use a supported browser - Chrome, Firefox, Edge or Safari
• Disable extensions - Adblockers and privacy extensions can cause problems
• Check server status - Many problems are temporary and server-related

Need help?

If these solutions do not work, contact your hosting provider customer service.

Related articles

• Roundcube webmail guide - Comprehensive user guide
• Roundcube contacts and address book - Manage contacts
• Set up Roundcube filters - Auto-sort emails
• Webmail error messages - General webmail problems
• IMAP vs POP3: what is the difference? - Choose the right protocol

Frequently Asked Questions

How long does it take to implement this?

Implementation time varies per situation. Simple configurations can be done within an hour, more complex setups may take several hours to a day.

What are the costs?

Costs depend on your hosting provider and package. Many basic features are included for free, advanced features may incur additional costs.

Do I need technical knowledge?

You need little technical knowledge for the basics. Most hosting providers offer extensive documentation and support to help you.