Despite having set the default Visitor entity to Contact, we occasionally find that a Lead is created, apparently by ClickDimensions, and we cannot find any reason for this.

It tends to be with (test) contacts with made up email addresses but it has also happened with real email addresses too.

Has anyone got any idea why this might be happening?  Fields are mapped to both the Lead and Contact entities by default but we didn't (yet) want to go through them and create new ones as once the mapping to Lead is there, it cannot be removed.