Frequently Asked Questions

Answers to common questions about Exchange Sync Bridge.

What is Exchange Sync Bridge?

Exchange Sync Bridge is an EWS-to-Microsoft Graph translation service. It allows existing software that still sends EWS-style Exchange Sync requests to continue working by translating supported requests into Microsoft Graph API calls behind the scenes.

Why is Exchange Sync Bridge needed?

Microsoft is retiring Exchange Web Services in Exchange Online. Many existing applications still use EWS for Exchange Sync. If those applications are not updated to use Microsoft's newer Graph-based technology, their sync features will stop working as Microsoft blocks the original access method.

Does ESB store mailbox, calendar, contact, or task data?

No. ESB does not store mailbox, calendar, contact, or task data. It translates supported requests, passes them to Microsoft 365, receives the response, translates it back, and returns it to your software.

What customer data does ESB store?

Renfield Software stores customer contact information, subscription information, licensed user information needed for billing, and technical tenant/installation information required to operate the service.

Do users sign into Exchange Sync Bridge?

No. There is no ESB login screen for end users and no ESB username/password. The one human authentication step is Microsoft 365 admin consent during onboarding.

How does Microsoft 365 authorization work?

Your Microsoft 365 administrator approves the Exchange Sync Bridge enterprise application through Microsoft's standard admin consent process. ESB then uses Microsoft Graph application permissions and the OAuth2 client-credentials flow for authorized sync requests.

Is this delegated user access or app-only access?

It is app-only access. ESB does not perform a separate OAuth exchange for each mailbox and does not pass through each user's Microsoft credentials.

How does ESB know which mailbox to sync?

The EWS request identifies the target mailbox. ESB reads that mailbox identifier and uses it when making the corresponding Microsoft Graph request.

Can ESB access every mailbox in the tenant?

After admin consent, the application has the Microsoft Graph permissions approved for the tenant. The current model should be understood as install-level trust. If your organization requires mailbox-level isolation inside the same tenant, contact Renfield Software before deployment.

What is the difference between Cloud Hosted and Customer-Hosted?

Cloud Hosted is operated by Renfield Software on Amazon Web Services and is intended to be the simplest deployment. Customer-Hosted requires installing a Windows service on a server you control and is intended for customers who want control over the relay environment.

How long does setup take?

For Cloud Hosted, setup can often be completed in minutes once the Microsoft 365 administrator is available. The main steps are Microsoft approval, license redemption, install API key issuance, and updating the client software's Exchange Sync settings.

Does the existing software need to support Microsoft Graph?

No. That is the point of Exchange Sync Bridge. Your existing software continues speaking EWS-style sync. ESB translates supported requests to Microsoft Graph.

Does ESB work with every EWS application?

ESB is designed for software that uses supported EWS-style sync requests. Because EWS is broad and applications use it differently, compatibility depends on the specific sync behavior of your software.

How is billing calculated?

Billing is based on the number of users configured to use Exchange Sync in the client application. The monthly charge adjusts based on the current sync-enabled user count as of the renewal date. Users added or removed during a month will be charged or credited on a prorated basis.

Can I suspend the service?

Yes. You can suspend monthly renewal at any time. Service continues until the next renewal date and then ends with no additional subscription charges. Suspended accounts may be reactivated later.

Is Customer-Hosted available now?

Customer-Hosted may be available at launch or may be offered later. Contact Renfield Software if your organization requires a customer-controlled deployment.

Are consultants allowed to resell ESB?

No, not at this time. Customers purchase directly from Renfield Software. Consultants may recommend ESB and may help customers with evaluation or setup.