Adding Outlook email that originates from an internal employee, to a case

Hi,

I can’t find this topic on the community, but I have a customer that uses cases for both internal and customer issues.

When an email comes into their outlook inbox from an external contact, they are able to add that email to an existing case using the outlook add in. But when an email hits their inbox from an internal employee, they are not able add that employee’s email to a case (even if they change the “Person” to a different name).

Am I missing something?

Thanks!