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How do I create a Connector in Microsoft 365?

If you are experiencing deliverability issues in Office 365, you may need to set up a Connector in Office 365.

Note: The following method of safelisting has been deprecated as of 09/01/2021. You will want to implement the new advanced delivery rules for Office 365 clients. If you implement the new rules and still experience bounced emails, follow the steps in this article. 

Create a connector

The connector is necessary to get around graylisting which Microsoft has implemented on the Portal simulated phishing emails (for more information on graylisting, see article: Fix email delivery issues for error code 451 4.7.500-699 (ASxxx) in Exchange Online).

To set up a Connector, navigate to the Office 365 Admin Center.


Once in the admin center, click 'Show all' then 'Exchange'.

show-all.png             exchange-menu.png

Under the mail flow section, click 'connectors'.


After navigating to connectors, click the 'Add a connector' button to add an additional connector. This will open the New Connector wizard.

In the 'Connection from:' select menu, select 'Partner Organization'.

In the 'Connection to:' select menu, select 'Office 365'.


Click 'Next' to navigate to the next step.

In the 'Name' text field, enter a descriptive name for the connector, such as 'Portal Connector'. Adding a connector description is optional. Make sure the 'Turn it on' checkbox is checked.


Click 'Next' to proceed to the next step.

Click the 'By verifying that the IP address...' radio button.

Add all necessary IP addresses. PhishingBox mail server IP addresses below.

US - Phishing Mail


US - System Mail


EU - Phishing Mail


EU - System Mail



Click 'Next' to proceed to the next step.

Ensure the 'Reject email messages if they aren't sent over TLS' checkbox is checked, then click 'Next' to navigate to the last step.


On the final page, review the connector's settings and click 'Create connector' to enable the connector.