How to sync the Global Address List (GAL) to mobile phones in Microsoft 365

The problem in one sentence

Microsoft 365 users can search the Global Address List (GAL) inside Outlook, but those directory entries never appear as contacts on the phone — so inbound calls show as unknown numbers, the dialer can’t autocomplete colleagues, and messaging apps can’t suggest names.

This is because the GAL lives in Exchange Online as a directory query against Entra ID (Azure AD), not as real contact objects in anyone’s mailbox. The native iOS and Android contacts apps only read the Contacts folder of each account — they have no mechanism to walk a company directory.

The four supported ways to fix it

There are only four architectures that actually push the GAL to phones. Every third-party product on the market is one of these four underneath.

1. Manual Outlook export (doesn’t scale)

Users can right-click a GAL entry in Outlook and choose Add to Contacts. It works for two or three colleagues. For a 200-person company it’s unusable, and entries drift out of date the moment someone changes phone numbers.

2. Legacy EWS PowerShell scripts (deprecated)

For years, IT admins wrote scheduled PowerShell scripts that used Exchange Web Services (EWS) to impersonate each user and write contacts into their mailbox. This works, but:

• EWS is being turned off on October 1, 2026. See our EWS deprecation migration guide for the full timeline.
• Scripts need impersonation rights, cert rotation, and constant babysitting.
• No UI, no monitoring, no delta sync — every run hits Exchange with a full scan.

3. Cloud SaaS contact-sync services

Vendors like CiraSync and sync.blue run the sync in their own cloud. This works, but it means:

• Your directory data leaves your tenant. For many regulated industries (healthcare, finance, government) that’s a compliance non-starter.
• Pricing is typically reported around ~$5/user/month — roughly 17× more expensive than on-premise alternatives. (Vendors rarely publish rates; always ask for a current quote.)
• You depend on a third-party SaaS uptime for every sync cycle.

4. Self-hosted Microsoft Graph API sync (recommended)

Run a Windows Service inside your own environment that calls Microsoft Graph and writes contacts directly into each user’s Exchange Online mailbox. This is what CYNC does. The service uses app-only authentication with a certificate, delta queries to sync only what changed, and JSON batching to stay well under Graph throttling limits.

Data never leaves the customer’s tenant. The first 10 users are free forever, which covers most small businesses at zero cost.

How Graph-based sync actually works on the phone

Once a contact exists in a user’s Exchange Online Contacts folder, the existing Exchange ActiveSync channel that their phone already uses for email and calendar also syncs contacts. No MDM profile changes, no app installs on the phone, no user training.

1. CYNC reads Entra ID users through Microsoft Graph (User.Read.All).
2. For each target mailbox, it writes/updates contacts via the Graph /me/contactFolders/... endpoint with Contacts.ReadWrite.
3. Exchange ActiveSync pushes the new contacts to every registered device.
4. iPhone and Android now show caller ID, dialer autocomplete, and messaging name resolution.

Decision matrix

Use this to pick the right option for your environment:

• Under 10 users? CYNC free tier. Zero cost, zero ongoing work.
• Regulated industry or data-residency rules? Self-hosted Graph sync (CYNC) — stays inside your tenant.
• Already using CiraSync and the bill is getting painful? See our CiraSync vs CYNC comparison.
• Still running EWS scripts? Migrate before October 2026 — start with our EWS migration guide.

Next steps

• CYNC getting-started guide — install and run the first sync in 15 minutes.
• Entra ID app registration walkthrough — exact Graph API permissions and certificate setup.
• Pricing calculator — work out the cost for any user count.