Sometimes you may find that an incoming message is not getting automatically mapped to a contact or client. This will be obvious as you will see the sender's address rather than a link to a client or contact.
The most common reason why this happens is because the address has been added to more than one client or contact in the platform. In that situation we don't know which one the message belongs to.
In this situation we would strongly recommend using relationships to make sure the email address is only mapped through to one single client or contact.