You are right! . . . with a bit of clarification. I bring all my email accounts into one email client (Mailbird), and that expanded information did not show in the Mailbird version. So, your solution prompted me to go online into my gmail account that I entered in the Simple Contact Form config, and the expanded information was there! Then, I went back into Mailbird and explored what would happen if I tried to reply to the Omeka.net email – and the “reply” automatically put in the sender’s email address, not the Omeka.net email address.
Suggestion: Put that info into the user guide. For example: In the notification email, expand the information in “To” and the sender’s “reply-to:” is listed. (Email clients may not show the “reply-to”; so you should try your email client’s “reply” to see if it populates “To” with the sender’s email, or you may need to go directly into your email account.)