Plesk webmail going down is one of the most disruptive failures a hosting provider can face. When clients can't access Roundcube or Horde, they can't read or send email — and support tickets flood in immediately. The frustrating part is that Plesk webmail failures often look identical on the surface (a login error or blank screen) but stem from completely different underlying causes.
This guide covers every common reason Plesk webmail stops working — from Dovecot service failures to Roundcube database corruption — and gives you the exact commands and steps to restore access fast.
Step 1: Identify the Error Type
The error message you see in the browser is your first diagnostic clue. Each message points to a specific cause:
- "Login Failed" — wrong credentials, or Dovecot IMAP service not running
- "CONNECTION FAILED" / "Database error" — Roundcube's local MySQL database is broken or missing
- "Connection to storage server failed" — Dovecot not listening on the expected port, or Plesk Premium Email extension conflict
- Blank white page or HTTP 500 — PHP error, SELinux policy, or missing Roundcube files
- "ssl_cert: Can't open file" — SSL certificate configured for mail is missing or unreadable
- Webmail loads but shows no emails — Dovecot running but IMAP connection timeout or maildir permission issue
💡 None of these worked? Skip the guesswork.
Get Expert Help →Step 2: Check Dovecot Status
Dovecot is the IMAP server that Roundcube connects to. If Dovecot is down or misconfigured, webmail login always fails — regardless of correct credentials.
systemctl status dovecot
# or on older systems:
service dovecot statusIf the service shows as failed or inactive, restart it:
systemctl restart dovecot
journalctl -u dovecot --since "10 minutes ago"ss -tlnp | grep dovecot
# Expected output should show port 993 (IMAP SSL) and 143 (IMAP)If Dovecot is listening on port 9993 instead of 993, this is caused by the Plesk Premium Email extension redirecting ports. See Step 7 for the fix.
tail -50 /var/log/maillog | grep -i "dovecot\|error\|fatal"
# Plesk-specific Dovecot log:
tail -50 /var/log/plesk/maillogopenssl s_client -connect localhost:993
# After connection, type:
a LOGIN user@yourdomain.com yourpasswordIf this returns NO [AUTHENTICATIONFAILED], Dovecot is up but rejecting the login. Check Dovecot's auth log:
grep "auth failed\|Login failed" /var/log/maillog | tail -20In Plesk go to Domains → yourdomain.com → Mail Accounts, select the account, and set a new password. Then test webmail login again.
plesk repair mail -yThis reconstructs Dovecot and Postfix configuration files from Plesk's database, fixing any configuration drift after upgrades.
Go to Domains → yourdomain.com → Mail Settings. Under SSL/TLS certificate for mail, set it to "Not selected" and click Apply. Then select the correct certificate again and click Apply.
This forces Plesk to regenerate the Dovecot SSL configuration with valid certificate paths.
plesk bin extension --exec letsencrypt cli.php -d yourdomain.com -m admin@yourdomain.comThen return to Mail Settings and assign the new certificate.
Step 6: Fix Blank Page or HTTP 500 Error
A blank white page or HTTP 500 error on the webmail URL is usually a PHP error or file permission issue.
1. Check Roundcube's PHP error log
tail -50 /var/log/roundcubemail/errors.log
# or check Apache/Nginx error log:
tail -50 /var/log/httpd/error_log
tail -50 /var/log/nginx/error.loggetenforce
# If "Enforcing", test temporarily with:
setenforce 0
# Then retry webmail. If this fixes it, add the proper SELinux policy instead of disabling entirely.chown -R apache:apache /usr/share/roundcubemail/
find /usr/share/roundcubemail/ -type d -exec chmod 755 {} \;
find /usr/share/roundcubemail/ -type f -exec chmod 644 {} \;plesk bin extension --list | grep -i premiumIn Plesk go to Extensions → My Extensions → Plesk Premium Email → Remove. Removing this extension restores Dovecot to port 993.
systemctl restart dovecot
ss -tlnp | grep dovecot # should show :993 nowStep 8: Fix Webmail After Plesk Upgrade
Plesk upgrades occasionally break webmail by overwriting Roundcube configuration or resetting database permissions. Run the full Plesk repair suite after any upgrade where webmail stops working:
# Repair all Plesk components
plesk repair all -y
# Specifically repair mail components
plesk repair mail -y
# Reinstall Roundcube database
plesk sbin roundcube_conf --reconfigureIf roundcube_conf is not available, use the Plesk UI to reinstall the Roundcube component as described in Step 3.
Step 9: Check Firewall — Port 993 Must Be Open
Roundcube connects to Dovecot on the same server, so firewall rules rarely block it. However, if you've recently applied firewall rules or migrated the server, confirm port 993 is accessible:
# CSF (most cPanel-adjacent Plesk installs)
csf -l | grep "993"
# iptables
iptables -L INPUT -n | grep 993
# firewalld (CentOS/RHEL 7+)
firewall-cmd --list-ports | grep 993If port 993 is not listed, add it:
firewall-cmd --permanent --add-port=993/tcp && firewall-cmd --reloadStep 10: Preventive Maintenance for Plesk Webmail
Webmail failures almost always have a warning sign before they become outages. Build these checks into your monthly server maintenance routine:
- Run
plesk repair mail -yafter every Plesk upgrade - Monitor the Dovecot service with your monitoring stack (Zabbix, Nagios, UptimeRobot)
- Renew SSL certificates before expiry — Dovecot stops accepting connections when the mail certificate expires
- Keep Roundcube updated via Plesk's component manager to prevent database schema incompatibilities
- Test webmail login after any firewall rule changes
For hosting companies managing dozens of Plesk servers, having a dedicated server management partner means webmail and mail delivery issues are caught by proactive monitoring before clients notice — not after tickets pile up.