When you use the Microsoft Outlook "Message Option" to look at an email header - is the email actually "opened" and susceptible to tracking if the sender is using a 3rd party tracking tool?
Email is tracked via return receipts, embedded images, or by clicking links embedded in the email.
By default, Outlook does not send read receipts without asking and it does not display embedded images when previewing an email.
Typically if the sender has been added to your safe sender’s list Outlook will handle the email differently and automatically display embedded images during preview.
So, assuming you don’t view the embedded images, send a read-receipt, or click any links while viewing the message headers, NO, you cannot be tracked by simply viewing email headers.
Automatically displaying embedded images is probably the single biggest mistake people make that allows them to be tracked.
If you’d like to check your Outlook trust settings and confirm how it handles embedded images you can read here: https://support.office.com/en-us/article/block-or-unblock-automatic-picture-downloads-in-email-messages-15e08854-6808-49b1-9a0a-50b81f2d617a
The short answer is "No".
In fact, with Outlook 2010's default security settings, it should be safe to open any email in the Reading Pane without fear of getting infected by any attachment, script or revealing that you opened the email to the original sender.
For those not familiar with Outlook's Message Options, in Outlook 2007 and below, you used to be able to right-click on any message in your inbox and select Message Options from the context pop-up menu.
Clicking Message Options shows the dialog box for a selected message so that you can change advanced options for the message such as Category or Importance. Just as important, at the bottom is a scroll-able field showing the message's Internet headers.
Message headers contain a lot of information such as the real address of the sender (not the one you see in the From field since that can be easily falsified), the sender's local time zone, the Email client from which the message was sent, the servers that the email passed through.
As of Outlook 2010 and above, Microsoft removed Message Options from the right click context menu.
If you still want to see the email header without opening the message or viewing it in the Reading Pane, you can add the Message Options button to your Quick Access Toolbar. How to do just that can be found by clicking here and then following the instructions under By leaving the message closed.