How do I find missing messages sent to a Microsoft Office 365 customer?

Customers who send or forward mail to domain names hosted by the Microsoft Office 365 email service occasionally report that the recipient can’t find the message.

The first thing to do if this happens is for the recipient to look in their “spam” folder.

If it’s not there, though, the recipient can ask the administrator of their Office 365 account to “trace” a message to see exactly what happened to it. This Microsoft page explains how they can do that.