Set up connectors for secure mail flow with a partner organization in Exchange Online

You can create connectors to apply security restrictions to mail exchanges with a partner organization. A partner can be an organization you do business with, such as a bank. It can also be a third-party cloud service that provides services such as archiving, anti-spam, and filtering.

You can create a connector to enforce encryption via transport layer security (TLS). You can also apply other security restrictions such as specifying domain names or IP address ranges that your partner organization sends mail from.

If email messages don't meet the security restrictions that you specify, the messages will be rejected.

For more information on setting up, using, and managing connectors for mails exchange, see:

• Set up a connector to apply security restrictions to mail sent from Microsoft 365 or Office 365 to your partner organization
• Set up a connector to apply security restrictions to mail sent from your partner organization to Microsoft 365 or Office 365
• Change a connector that Microsoft 365 or Office 365 is using for mail flow
• Examples of connector configurations for securing email exchange between Microsoft 365 or Office 365 and your partner organization

If you use a third-party cloud service for email filtering and need instructions for making this work with Microsoft 365 or Office 365, see Mail flow best practices for Exchange Online and Microsoft 365 or Office 365 (overview).

Configure mail flow using connectors in Microsoft 365 or Office 365

Mail flow best practices for Exchange Online, Microsoft 365, and Office 365 (overview)

Validate connectors

What happens when I have multiple connectors for the same scenario?