You sent your mailing with a From line of "Jane" <firstname.lastname@example.org>. But, the copy you received instead displayed "Marketing" <email@example.com>.
The receiving server interprets the From line and because your server has the Sender name for firstname.lastname@example.org set as Marketing, Jane is not displayed.
Although rare, it may happen that the receiving server, say a Microsoft Exchange system, already has a particular email address set up with a particular Sender name. In this case, essentially the receiving server says "Oh, we already know who that address is, so we'll display the name that we have, rather than what is being sent in the header of the mailing."