Controlled calendar replication across Microsoft 365 and Google.
MCS Calendar Relay synchronizes Microsoft 365 Group, user, and shared-mailbox calendars to Microsoft 365 or Google Calendar destinations without exposing source calendars, granting unnecessary access, or relying on manual duplication.
Publish calendar information without opening the source.
Organizations often need to make calendar information available to another team, system, tenant, or platform. MCS Calendar Relay creates controlled, one-way copies of calendar events while keeping the source calendar authoritative and protected.
Microsoft 365 sources
- Microsoft 365 Group calendars
- User mailbox calendars
- Shared-mailbox calendars
- Approved source-calendar controls
- Rolling past and future synchronization windows
Flexible destinations
- Microsoft 365 mailbox calendars
- Personal Gmail calendars
- Google Workspace calendars
- Shared Google calendars
- Custom-domain Google Workspace environments
A simple, controlled synchronization process.
Each relay connects one approved Microsoft 365 source calendar to one destination calendar and keeps the destination current on a schedule you control.
1. Approve
Select the Microsoft 365 calendars that administrators are allowed to use as relay sources.
2. Connect
Choose a Microsoft 365 or Google destination and verify that the connection can create and update events.
3. Configure
Set the sync interval, past-day window, future-day window, destination calendar, and dry-run mode.
4. Synchronize
New events are created once, existing events are updated, and removed source events are handled according to policy.
Rolling synchronization windows
A relay configured for 90 past days and 365 future days recalculates that window each time it runs. The window moves forward continuously until the relay is paused or removed.
Persistent event mappings
MCS Calendar Relay stores source-to-destination event relationships so existing events are updated in place instead of recreated on every run.
Built for operational use, not one-time exports.
Synchronization controls
- Create, update, and remove mirrored events
- Configurable synchronization intervals
- Dry-run testing before activation
- Manual synchronization for testing and recovery
- Duplicate-prevention through event mappings
- Per-relay rolling date windows
Administration and governance
- Multi-organization management
- Microsoft Entra ID sign-in
- Role-based administrative access
- Approved calendar catalogs
- Organization-level user assignments
- Audit logging and synchronization history
Microsoft 365 support
- Microsoft 365 Group calendar sources
- User and shared-mailbox sources
- Microsoft 365 destination calendars
- Application-based background synchronization
- Approved source and destination controls
- Optional destination-calendar cleanup
Google Calendar support
- Personal Gmail calendar destinations
- Google Workspace user calendars
- Shared Google calendars
- Service-account access
- Google OAuth user authorization
- Domain-wide delegation for managed Workspace tenants
Event handling
- Subject, body, location, start, and end time
- Teams links preserved in event details
- Source updates reflected at the destination
- Deleted source events removed by policy
- Recurring-event support
- Destination event IDs tracked for reliable updates
Designed to avoid disruption
- One-way replication protects source calendars
- No attendee invitations by default
- No automatic Google Meet creation
- No modification of the source calendar
- Destination calendars remain independently accessible
- Dry-run validation before live writes
Useful anywhere calendar data must cross a boundary.
Public-sector publishing
Mirror briefing, meeting, public-information, emergency-management, or operational calendars into a controlled destination without granting access to the source.
Cross-platform organizations
Publish Microsoft 365 calendar information to teams that work in Google Workspace or personal Gmail without maintaining duplicate events by hand.
Executive and departmental views
Create simplified destination calendars for leadership, departments, shared workgroups, public displays, or downstream systems.
Tenant-to-tenant transitions
Maintain calendar visibility during migrations, organizational changes, mergers, acquisitions, or phased Microsoft 365 deployments.
Shared operational calendars
Replicate source calendars into shared operational views without exposing mailbox permissions or granting broad Graph access to end users.
External collaboration
Provide partners, vendors, boards, or outside teams with a controlled calendar copy while keeping internal scheduling systems private.
Designed around least privilege and administrative control.
Calendar replication should not require users to browse every mailbox, expose source calendars, or share credentials across systems.
Identity and access
- Microsoft Entra ID authentication
- Platform and organization-level administration
- Role-based access to users, calendars, and relays
- Users cannot change their own role
- Approved source-calendar restrictions
- Organization-scoped configuration and history
Credential protection
- Encrypted tenant and provider credentials
- Separate interactive and background identities
- Support for Google OAuth refresh tokens
- Support for Google service accounts
- Certificate-based Microsoft authentication roadmap
- Secret rotation and access-scoping guidance
Auditability
- User assignment and role-change logging
- Calendar approval history
- Relay creation and deletion records
- Manual and scheduled run history
- Destination-calendar deletion safeguards
- Administrative activity tracking
Safe deletion behavior
- Delete relay configuration without deleting calendars
- Optional cleanup of application-created destinations
- Confirmation required before destructive actions
- Shared destinations protected from accidental removal
- Google cleanup limited to tracked relay events
- Source calendars are never deleted by a relay
Support for personal Gmail and managed Google Workspace.
Personal Gmail and individual users
- User-authorized Google OAuth connection
- Encrypted refresh-token storage
- Access to calendars writable by the connected account
- Suitable for personal Gmail and individual Workspace users
- No Google administrator required for ordinary OAuth use
Google Workspace organizations
- Service-account connections
- Shared-calendar access
- Domain-wide delegation
- Impersonation of an approved Workspace account
- Administrative control over available calendars
Shared Google calendars
A Google calendar can be shared directly with the service-account email address and granted permission to make changes to events. This is useful for a small number of managed destination calendars.
Custom-domain Workspace accounts
Google Workspace accounts using a custom domain can connect through individual OAuth or through domain-wide delegation for centralized, unattended organizational access.
Deploy on premises, in a private cloud, or as a managed environment.
On-premises
- Debian or compatible Linux server
- Apache and PHP-FPM
- MariaDB or MySQL
- Customer-controlled credentials and data
Private cloud
- Customer-managed virtual machine
- Private network placement
- Organization-controlled DNS and certificates
- Integration with existing monitoring and backup tools
Managed deployment
- Implementation assistance
- Microsoft and Google configuration support
- Upgrade and maintenance options
- Operational support plans
Implementation services
- Environment validation
- Microsoft Entra application setup
- Microsoft Graph permissions configuration
- Google Cloud and Workspace setup
- Initial relay configuration and testing
- Administrator handoff and documentation
Operational readiness
- Dry-run validation
- Connection testing
- Audit and history review
- Backup and recovery guidance
- Log rotation and health checks
- Production cutover support
Choose the deployment that fits your organization.
Start small, expand as requirements grow, and keep calendar replication under your organization’s control.
Community
Free
For evaluation, labs, and small internal deployments.
- Up to 2 relay jobs
- Microsoft 365 destinations
- Manual and scheduled synchronization
- Community documentation
Professional
$299 perpetual
or $29 per month
- Up to 10 relay jobs
- Microsoft 365 and Google destinations
- Role-based administration
- Audit history
Business
$799 perpetual
or $69 per month
- Up to 50 relay jobs
- Multiple organizations
- Google Workspace support
- Priority support
Government
$995 per year
- Up to 25 relay jobs
- Public-sector deployment guidance
- Microsoft 365 and Google support
- Security and audit-focused configuration
Enterprise
From $2,500 per year
- Custom relay limits
- Multi-tenant administration
- Google Workspace delegation
- Implementation and support options
Final pricing may vary based on deployment scope, support requirements, hosting model, and integration complexity.
Practical support for deployment and operations.
Available services
- Installation assistance
- Microsoft 365 configuration
- Google Calendar and Workspace configuration
- Migration and upgrade assistance
- Relay troubleshooting
- Custom integration planning
Future development direction
- Delta-based synchronization
- Expanded recurring-event handling
- Advanced notification and reporting
- Provider-neutral destination architecture
- Exchange mail-contact management
- Broader MCS Relay platform capabilities
Connect the calendars your organization depends on.
Clear scope, practical recommendations, and controlled Microsoft 365 and Google integration.