Hi Russell,
>> I would like to view the email address before opening my email.
We may try to display the sender’s e-mail address as a column in the message list by using a custom form configuration file:

For the form configuration file and detailed instructions, you may refer the the following article:
https://www.howto-outlook.com/howto/viewsenderaddress.htm
Please Note: Since the web site is not hosted by Microsoft, the link may change without notice. Microsoft does not guarantee the accuracy of this information.
Hope this can be helpful.
Best regards,
Yuki Sun
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