Hey Johnnie!
This would be possible by adding custom CSS to the Personalization section in the Sys Admin settings. I'm slightly familiar with CSS so I looked into this a bit, but I was unfortunately unable to figure this one out. From what I can tell, you won't be able to remove just "SmarterMail Enterprise 15.2" but the entire right side of the footer text.
Are you familiar with using CSS?
Andrea Free
SmarterTools Inc.
877-357-6278
www.smartertools.com