Allowlisting - Avoid Email Deferral/Delays By Configuring An Inbound Connector In Microsoft 365

Overview

If Microsoft 365 is delaying emails from our platform, it usually means Microsoft has temporarily throttled emails from the sending IP (delays can be up to 24 hours). Microsoft recommends creating a connector to trust the sending service and remove this throttling.

How to create a connector in Microsoft 365

To ensure reliable email delivery, create a connector in Microsoft 365 that allows messages from our platform to be trusted and accepted.

1. Open the Exchange Admin Center.
2. In the left-hand menu, expand Mail flow, then select Connectors.
3. Click Add a connector.
4. Configure the connector type as follows, then click Next:

• Connection from: Partner organization
• Connection to: Office 365

5. Enter a name for the connector, such as: CanIPhish Email Connector

Note: You can also add an optional description. Make sure Turn it on is enabled, then click Next.

6. On the "How should Office 365 identify email from your partner organization?" screen, choose:

• By verifying that the IP address of the sending server matches one of the following IP addresses
• Add the following IP addresses:
  • 3.106.21.22
  • 13.237.47.221

Then click Next.
7. On the security restrictions screen, enable the following setting, then click Next:

• Reject email messages if they aren't sent over TLS

8. Review the configuration, then click Create connector.

What this does

This connector tells Microsoft 365 to trust messages sent from our platform when they come from the approved IP addresses and are delivered securely over TLS. This helps prevent messages from being delayed unnecessarily. Microsoft specifically recommends configuring a connector when inbound mail is routed through a third-party service.

After you finish

Allow a few minutes for the connector to become active, then send a test email to confirm delivery is working as expected.

Any emails that have already been sent and are in a delayed state will be received over the following 30 minutes as they are flushed from a queue of delayed emails.