Emails won't send when I hit reply

I’ve tried hitting reply, and reply all to different emails… but nothing will send. (Not just to one person… it won’t send to multiple different emails). It’s strange because the email will show up in my sent inbox like it has sent but obviously something is wrong because the person isn’t receiving the email. The only way I can send an email successfully is if I hit new. Any idea what’s wrong? 

I just came across this. It seems if you set a template for replies it exhibits this behavior.

Ok. How do I delete this template?