iPhone 5 mail broken/ frozen

I have an iPhone 5 and since trying to send an email with too many attachments, my mail screen has been frozen white, with only a little 'write new message' icon visible in the corner. It isn't loading anything at all, and has been this way for several hours now, can anybody help me? The app also closes itself and tries to reboot, but then closes again. I have already tried rebooting, resetting my settings and checking that I have the correct mail settings through the apple website. I have also checked that my email account is functioning online, on my computer and everything is fine.