Microsoft 365 does not natively push the Global Address List (GAL) or shared contacts to mobile devices in a consistent, enterprise‑friendly way. As a result, IT teams often turn to third‑party solutions like CiraSync or Contactzilla to ensure employees have accurate, up‑to‑date contact information on their phones. 

While both platforms solve the same underlying problem, they take very different architectural approaches. This comparison breaks down CiraSync vs Contactzilla to help IT leaders determine which solution best fits their Microsoft 365 environment, security requirements, and device management strategy. 

What Is CiraSync? 

CiraSync is an enterprise SaaS platform designed specifically for Microsoft 365 contact and calendar synchronization. It uses Microsoft 365 (Exchange Online and Entra ID) as the system of record, then automatically syncs GAL contacts, CRM contacts, and shared calendars directly into native iOS and Android apps. 

CiraSync is centrally deployed and managed by IT, with no end‑user setup and no user authentication required. Sync runs automatically in the background once configured. 

Key characteristics of CiraSync: 

• Purpose‑built for Microsoft 365 environments 
• Syncs contacts and calendars 
• One‑way sync preserves Microsoft 365 as the source of truth 
• Centralized, role‑based admin control 
• Hosted on Microsoft Azure 
• SOC 2 and GDPR aligned 
• Works with or without MDM, depending on deployment model 

Important Clarification: How CiraSync Syncs to Mobile Devices 

CiraSync supports two deployment paths, depending on whether the customer uses MDM: 

With MDM (CardDAV) 

1. 1. Contacts can be pushed directly to devices using CardDAV. 
   2. No mobile app is required. 
   3. CardDAV does require an MDM solution. 
   4. Currently supports Intune, with AirWatch (Workspace ONE) and SOTI support coming soon.  

Without MDM (Mailbox‑based sync) 

1. Contacts are written into the user’s Microsoft 365 mailbox. 
2. A mobile app is required to access those contacts – typically Outlook Mobile or the native iOS Mail app. 

This ensures CiraSync works for both MDM‑managed fleets and BYOD environments. 

What Is Contactzilla? 

Contactzilla is a contact management and distribution platform focused on shared address books that sync to mobile devices using CardDAV and MDM‑friendly deployment models. Instead of writing contacts into individual Microsoft 365 mailboxes, Contactzilla maintains a central shared address book and pushes contacts directly to iOS and Android devices. 

Contactzilla is commonly used in MDM‑managed fleets, where read‑only access and device‑level control are required. 

Key characteristics of Contactzilla: 

• Central shared contact lists 
• Mobile‑first contact deployment 
• CardDAV‑based sync 
• Strong MDM integration (Jamf, Intune, etc.) 
• Read‑only and label‑based permissions 
• SOC 2, GDPR, and HIPAA compliance 
• Contact‑only focus (no calendar sync) 

CiraSync vs Contactzilla: Feature Comparison 

Side‑by‑Side Comparison Table 

Key Architectural Differences That Matter 

1. Microsoft 365 Mailbox Sync vs Shared Address Book Model

CiraSync writes contacts into each user’s mailbox (when MDM is not available), allowing Exchange and native mobile sync to deliver contacts automatically. This approach is tightly integrated with Microsoft 365 and works in BYOD or mixed‑device environments. 

Contactzilla avoids mailbox writes entirely. Instead, it maintains a central address book and distributes contacts directly to devices using CardDAV and MDM profiles. 

2. Calendar Support vs Contact‑Only Focus

CiraSync supports shared calendar and public calendar sync – critical for organizations needing mobile access to schedules, resources, or on‑call rotations. 

Contactzilla focuses exclusively on contact distribution and does not provide calendar synchronization. 

3. MDM‑Centric vs Microsoft‑Centric Deployments

Contactzilla is designed for environments with: 

• MDM‑managed devices 
• Read‑only contact requirements 
• Shared or frontline phones 

CiraSync is designed for: 

• Microsoft 365‑centric enterprises 
• Knowledge workers 
• BYOD and mixed device environments 
• Organizations that may or may not use MDM 

Which Solution Is Right for Your Organization? 

Choose CiraSync if you: 

• Run primarily on Microsoft 365 
• Need contacts and calendars on mobile 
• Want Microsoft 365 as the single source of truth 
• Prefer not to rely on MDM 
• Need centralized, tenant‑wide control 
• Support BYOD or mixed device environments 

Choose Contactzilla if you: 

• Manage MDM‑controlled device fleets 
• Need read‑only shared contact lists 
• Support frontline or shared‑device users 
• Want device‑level contact distribution without mailbox writes