On ticket view I no longer see From/To/CC email addresses on the top of the message (between title of the mail and just before its content, near action buttons).
Previously the migration to OTRS 6, this kind of information were visible.
That's particularly useful when we've to deal with tickets merged from a queue (dest email) to another.
Like https://ticket.wikimedia.org/otrs/index.pl?Action=AgentTicketZoom;TicketID=11506123, it is not possible to see in the view that an email were in CC. I have to use Text format view and search in the headers, that is not a useful way to do. Btw thanks for the migration :)