Frequently Asked Questions.

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.

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.

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.

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

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.

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.

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.

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

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.

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.

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, and entering the connection details in your vendor software: the Connection URL, Client ID, Tenant ID, and Secret Value. Once those values are saved, your existing software connects to Exchange through Exchange Sync Bridge with no additional install or service required.

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

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.

Billing is based on the number of sync-enabled users you license. If you enable sync for more users than licensed, service continues uninterrupted — your license count, and billing, adjusts automatically at your next renewal. You can also reduce your license count at any time; the change takes effect at your next renewal.

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.

Customer-Hosted is coming soon. Contact us for more information.

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

Microsoft has published technical documentation about the Exchange Web Services retirement in Exchange Online. You can read the official statement here.