Do I need to create a connector in Exchange Online?

Find your mail flow scenario to see if you need to create a connector for your Exchange Online organization.

Scenario Description Connector required? Connector settings
You have a standalone EOP subscription. You have your own on-premises email servers, and you subscribe to EOP only for email protection services for your on-premises mailboxes (you have no mailboxes in Exchange Online).

For more information, see the topic Exchange Online Protection overview and How connectors work with my on-premises email servers.
Yes Connector for incoming email:
From: Your on-premises email server
To: Office 365

Connector for outgoing email:
From: Office 365
To: Your on-premises mail server
Some of your mailboxes are on your on-premises email servers, and some are in Exchange Online. Before you manually configure connectors, check whether an Exchange hybrid deployment better meets your business needs.
For details, see I have my own email servers and Exchange Server Hybrid Deployments.
Yes Connector for incoming email:
From: Your on-premises email server
To: Office 365

Connector for outgoing email:
From: Office 365
To: Your on-premises email server
All of your mailboxes are in Exchange Online, but you need to send email from sources in your on-premises organization. You don't have your own email servers, but you need to send email from non-mailboxes: printers, fax machines, apps, or other devices.

For details, see Option 3: Configure a connector to send mail using Office 365 SMTP relay
Optional Only one connector for incoming email:
From: Your organization's email server
To: Office 365
You frequently exchange sensitive information with business partners, and you want to apply security restrictions. You want to use Transport Layer Security (TLS) to encrypt sensitive information or you want to limit the source (IP addresses) for email from the partner domain.

For details, see Set up connectors for secure mail flow with a partner organization.
Optional Connector for incoming email:
From: Partner organization
To: Office 365
Connector for outgoing email:
From: Office 365
• To: Partner organization

Note

For more information about these scenarios, see Configure mail flow using connectors in Office 365.