Local-first
The administrator controls the system that receives local SMTP and holds queued mail.
About the project
A focused answer to
a real compatibility problem.
RelayBridge is an independent open-source project for administrators who need working legacy devices to coexist with modern mail platforms, starting with Microsoft 365.
01 / WHY
Keep useful equipment useful.
Printers, scanners, appliances, and line-of-business systems often have a longer operational life than the authentication methods they were built around.
RelayBridge is designed to close that gap without asking every device to understand OAuth and without introducing a RelayBridge-operated cloud relay into the mail path.
02 / PRINCIPLES
Inspectability
Architecture, limitations, and source should be available for direct scrutiny.
Precision
Claims should match real protocol boundaries, especially around authorization and delivery.
03 / STATUS
Built in the open,
before calling it ready.
RelayBridge is under active development and v1.0 is being prepared. Public builds, complete setup instructions, and the final support matrix will be published only after the relevant implementation is ready.
04 / FUTURE
Future direction
Microsoft 365 is the first supported provider. RelayBridge is architected with potential future provider expansion in mind.
Google Workspace and other modern mail providers may be evaluated later. Future integrations will only be added when they meet RelayBridge's existing local-first, security, durability, and reliability standards.
Open source
Follow RelayBridge on GitHub.
Inspect public work, follow release preparation, and learn how the security model develops.