Yes, but I don't recommend doing so. You'll need to edit the define _UE_PREGMATCH_VALID_EMAIL in comprofiler.class.php and at the very end you'll see an "i" (without quotes), simply remove this and it removes case insensitive flag making only lowercase valid.
This doesn't seam logical however, this is a bug in your 3rd party extension which you're trying to fix through CB. You should contact the developer of your extension and have them fix their mailing function, capitals are completely valid in emails.