Reopening Closed Tickets

Currently we have the reopen resolved/closed incidents turned to off. However, if someone goes back into their email from an older ticket and just replies like a normal email, it will reopen the ticket no matter if it's closed or resolved. 

Is there a way to mitigate that? I know that the off feature for this is if someone goes into the solarwinds email and tries to add a comment, they can't do so.

Is there a way to prevent this from replying to a regular email since people can submit tickets that way as well? As much as I'd like to turn off the option to email tickets in, people don't like change so it's not feasible for us. 

Hopefully this makes sense.