If you are having problems with email messages bouncing (not delivering) in Office 365, please follow the steps below to add the sending email servers to the whitelist.
1. Log into your Office 365 and click on the Admin Portal.
2. Select Admin Centers -> Exchange.
3. Select Connection Filter under the Protection section.
4. Click Connection Filter, then click the Pencil icon to edit the connection filter policy.
5. Under the IP Allow list, click the + (plus) sign to add an IP address.
6. Add the following IP address:
7. Click OK, then Save.