We understand that you are having troubles with the Trend Micro program blocking the emails coming from the Office 365 applications.
This should not be the case unless the emails are classified as a Spam or contains a malicious link or attachment on it.
Can we have a screenshot of the detection or the said blocking message that you are seeing so we can check this from our end?
Furthermore, our Trend MIcro AntiSpam toolbars might be the one to detect these messages if you are using the Outlook email service. We also want to know what email service are you using and what version is it on so we can check for compatibility issues.
We are looking forward to your response and we hope that we can fix this for you as soon as possible.