Hi @AmyNiecikowski ...
Do you know if the student's e-mail address can be found using this Guide?
How do I view bounced email notifications for user... - Instructure Community (canvaslms.com)
If so, I've had similar situations in my former job. I was able to contact the Canvas Help Desk staff or someone from our Customer Success Team (I can't remember which) that was able to get the "!" removed ... since the e-mail address was also correct in our Canvas environment. Maybe this will work for you as well by having a conversation with Instructure staff.
Hope this helps a bit! Keep us posted.