Service Status

Scheduled Maintenance (High Priority Release) from 2026-09-27 20:00 BST to 2026-09-28 00:00 BST

Scheduled maintenance Zimbra Email and Collaboration Webmail Inbound Outbound Proxy Reseller Control Panel
2026-09-27 20:00 BST · 4 hours

Updates

Scheduled

We will be upgrading our Zimbra platform to the Zimbra Collaboration Suite (ZCS) v10.1.21 (Daffodil) release.

Service Disruption Expected

During this period there will be rolling restarts which will mean short periods of time when mailboxes are inaccessible.

https://wiki.zimbra.com/wiki/Zimbra_Releases/10.1.21 (release notes available after 24th September)

New Features

  • Mail Recall: Recall mis-sent internal emails from the Modern Web App or Zimbra Desktop within a configurable window, with automatic recipient notifications.
  • Revamped Language Module: 6,000+ UI translations issues proactively fixed; new native support for Bahasa Indonesia and Filipino (Tagalog); 50+ customer-reported translation issues resolved.
  • Self-Service Account Clean Up: Color-coded quota indicators, sort emails by size, and bulk-delete or move large emails to manage mailbox capacity independently without filing IT tickets.
  • S/MIME: Signed emails now include the full intermediate certificate chain for automatic validation by recipient clients.
  • Per-Domain IdP & SAML Routing: Each domain on your Zimbra instance can now have its own Identity Provider, with automatic user routing and fully isolated authentication metadata; eliminating cross-domain SSO conflicts.
Modern Web App UI Innovations:
  • Email Density & Customization: Relaxed, Regular, or Slim email view modes for detailed previews or high-volume scanning; Email Templates enabled by default; standardized tooltips across all modules.
  • Mail Productivity: Inline conversation reply, message redirect (resend, original sender preserved), 1-click folder creation with color-coding, thread expansion, and arrow-key navigation.
  • Calendar Workflows: Side-by-side multi-calendar day view, improved visual layout for overlapping events, 1-click Quick Event Create popover, and color-coded event tags.
  • Navigation & Onboarding: Modernized top bar (click any icon to reset view), interactive storage quota indicator, and built-in guided tour for first-time login.

Security and Platform Hardening

  • Password Recovery: Fixed a password recovery flaw that allowed unauthenticated attackers to predict recovery codes.
  • Authentication: Tightened WebDAV authentication logic (pre-MFA token validation).
  • Vulnerability Fixes: Fixed stored cross-site scripting (XSS) vulnerabilities in the Classic Web Client tied to email metadata handling.
  • Dependency Upgrades: Upgraded OpenJDK to 17.0.19 and updated NGINX security modules.

Maintenance & Platform Stability

  • Zimbra Connector for Outlook (ZCO): Fixed Outlook 2FA instability, MIME boundary failures, password-expiration prompts, and oversized attachment handling.
  • Server and System: Fixed IMAP file-descriptor leaks, automated Apache Tika temp-file cleanup, self-forwarding loops, and premature LDAP deletion on removal.
  • Webmail & Shared Folders: Fixed shared folder move/delete, unified trash behavior, restored cross-UI signature editing, corrected saved search sorting, and resolved print-preview freezing.
  • Additional Fixes: 50+ updates spanning third-party calendar URL generation, GAL autocomplete, and LDS license calculations for domain-level COS inheritance.
September 23, 2026 · 15:30 BST

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