What does Show As mean in Outlook?

“Angi angående” is the English “Set regarding”, and it answers the question: What is this email about?

What actually happens

The email is saved as an activity in Dynamics 365 and linked to the record you select. If someone opens that opportunity later, the email will appear on the timeline along with everything else that has happened.

Why tracking against the customer isn't enough

A customer may have five open cases and three sales opportunities at the same time. Emails linked only to the customer become an undifferentiated pile. Linked to the right case, they tell a story.

It works both ways

If the customer replies to an email that is already linked to a case, the reply is linked to the same case. That is why it pays to establish the link early in the conversation rather than clean things up afterward.