The below steps will walk you through adding HappyFox as a Safe Sender on your Office 365 (Microsoft Exchange) instance. This will help ensure your emails are delivered without any delays.
Step 1: Log on to your Office365 (Microsoft Exchange) instance, then head on over to the Exchange Admin Center >> Protection >> Connection Filter.
Step 2: On the pop-up window that appears, select "connection filtering". Under "IP Allow list", click the plus symbol (+) to add the HappyFox IP addresses under the Allowed IP Address section - 18.104.22.168, 22.214.171.124, 126.96.36.199,
Step 3: Click the check box next to "Enable safe list", and then click Save to confirm your settings.