JD_Toims - 5:24 am on Sep 12, 2013 (gmt 0)
Okay, well after copy/pasting your code into TextWrangler and looking at line 61 where you're getting the error and not seeing anything that should cause the error you're receiving my best guess is it's white-space on a line that's being output prior to the redirect.
The forum removes extra spaces, so I might not see it through a copy and paste even with "invisibles" turned on -- I could be missing something and if someone else sees it I hope they feel free to point it out, but if not, the first thing I would probably check for is an empty line that starts with [or contains] [space].
If that didn't work, I'd comment out everything between the $email_to + $email_subject lines and the $sent + if($sent) conditional -- Then if that worked I'd add functions/if's back in one at a time to find which is causing the issue. If the initial commenting didn't work and I still received an error I'd only have 8 or 10 lines of live code to look at and figure out the issue with.
BTW: Welcome [or welcome back to] WebmasterWorld!