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How to Configure Exchange Online SMTP Relay with a Partner Server
Question details
The user needs to configure Exchange Online SMTP relay to route mail through a partner organization's physical mail servers.
- Product
- Microsoft Exchange Online
- Device & OS
- not provided
- Scenario
- Routing email traffic securely between Microsoft 365 and a partner organization's email servers.
- Observed behavior
- Setting up an inbound connector matching the sending host's IP address or certificate domain is required for the SMTP relay to function.
Ensure you have global administrator or Exchange administrator privileges in the Microsoft 365 admin center before attempting to configure connectors or accepted domains.
Configure an Inbound Connector in Microsoft 365
Set up an inbound connector to securely accept and relay mail from the partner server.
Exchange Online requires a properly authenticated inbound connector to process relayed emails from third-party physical servers. This ensures your tenant only accepts authorized traffic.
Log in to the Microsoft 365 admin center and navigate to the Exchange Admin Center (EAC).
Go to Mail flow > Connectors. Click the '+' button to add a new connector. Choose 'Partner organization' as the source and 'Office 365' as the destination.
Configure the connector to authenticate the sender by matching the sending host's IP address or the domain name on their TLS (SMTP) certificate.
Ensure that the SMTP certificate domain, envelope sender domain, or header sender domain used by the partner is registered as an 'accepted domain' in your Microsoft 365 tenant.
Enhance Your Daily Productivity with WPS Office
While configuring Exchange Server routing requires Microsoft 365 admin access, managing your daily documents doesn't have to be complicated or expensive. WPS Office is a lightweight, free alternative that offers full compatibility with Microsoft Office files.
- 1. Visit the Official Website: Go to the WPS Office website to find the correct version for your operating system.
- 2. Download the Installer: Click the download button and wait for the lightweight installation package to finish downloading.
- 3. Install and Open Files: Run the installer, follow the on-screen instructions, and instantly open your Microsoft Office documents.
Frequently Asked Questions
Can a cloud-only organization configure SMTP relay with partner servers?
Yes. Even without on-premises servers, you can configure inbound connectors in Microsoft 365 to route mail securely between your cloud environment and a partner's email servers.
What authentication methods can be used for the inbound connector?
The inbound connector typically requires matching the sending host’s specific IP address or the domain name present on their TLS (SMTP) certificate to properly authenticate the partner server.
Why is the relay failing after setting up the connector?
Ensure that the SMTP certificate domain, envelope sender domain, or header sender domain is fully registered and verified as an 'accepted domain' in your Microsoft 365 tenant settings.
What should I do if the connector configuration is blocked in my admin center?
If you face specific configuration restrictions or errors as a cloud-only organization, you should contact your IT administrator to open a service request directly in the Microsoft 365 admin center for backend support.
