Confirm prerequisites
Before creating a device, Microsoft 365 must be active and verified during the current service start. Printer connectivity must show the intended private listener and queue as ready.
Complete the device wizard
- Name the device.Use a recognizable printer, scanner, appliance, or application name and an optional operational description.
- Choose authentication capability.Select Authenticated mode when the device supports SMTP AUTH LOGIN or AUTH PLAIN. Choose Legacy mode only when it cannot authenticate.
- Restrict the source.Enter the exact private source IP address or the narrowest required subnet.
- Review sender and endpoint.Confirm the one active authorized sender and the private RelayBridge address and port.
- Create and retain the setup values.Authenticated-mode credentials are shown once. Store the generated password securely before leaving the page.
RelayBridge stores only a password verifier and cannot display the original password later. Resetting a password immediately invalidates the old one.
Configure the SMTP client
| Device field | RelayBridge value |
|---|---|
| SMTP server | The private RelayBridge address displayed by the wizard |
| Port | The displayed printer SMTP port, normally 2525 |
| Connection security | None; inbound STARTTLS is unavailable in RC1 |
| Sender | The exact active Exchange Online sender mailbox |
| Authentication | Generated username and one-time password in Authenticated mode; none in Legacy mode |
| Source address | Must match the exact private address or subnet configured for this device |
Manufacturer field names differ. Use the device vendor's documentation to map these values without enabling unsupported TLS modes or changing the exact SMTP envelope sender.
Test with non-sensitive mail
Send a small synthetic message. A local SMTP success means RelayBridge durably accepted the message on this host. It does not mean Exchange Online or the inbox accepted it.
Use Diagnostics and queue state to confirm that a worker claimed the message and received a final Exchange response. Only a final Exchange 250 means Microsoft accepted the upstream SMTP transaction; later filtering, routing, quarantine, and inbox placement remain separate.