Need to make sure your mail-tags all match exactly or else it stops working

I was having serious troubles getting one of my contact forms to work and found one slight error I had made: a mismatch between a mail-tag in the Form tab (of the editing section) and the mail-tag in the Mail tab (of the editing section). I found that if there is any mismatch between the mail-tags in the two tabs, the email simply disappears into the void. It will give you a “Sent successfully” message, but it never makes it to the recipient’s inbox.