Identify emails with external address in cc list

[Stuart]

Does anyone know of a way to identify emails (incoming and outgoing)
that are a mix of internal company recipients and external?

i.e.:

1) Outgoing emails from me that contain even a single recipient
outside my company (internal address are all (e-mail address removed))
(whether To, CC or BCC)

2) Incoming emails to me that contain even a single other recipient
from outside my company (whether To, CC or BCC)

Identifying incoming emails FROM external senders is simple, but can't
work out how to do this?

Grateful for any suggestions!

Stuart