Hiri is all about getting your mail under control and spending less time managing your mail. One of the features that seems to confuse people at first but makes sense when you get it is that we put the subject line at the bottom of the email.
When we were making Hiri, we looked at a LOT of research about email and productivity and found that people write better subject lines when they write them after they've written the content. Same goes for any writing really - writers pick the titles for their books only after they've finished writing the content. And it makes sense. How often does it happen that the email you've written is actually completely different from the idea you started it with? You add stuff, you change stuff, and the subject line should reflect that. It is a short summary of what the email is all about.
Besides, even though you read your email from subject to content, that doesn't mean that you need to write it in that order. Just the opposite.
Better subject line means less time spent trying to understand what the email is all about for the person on the other end. If the people you email also use Hiri, you'll see this benefit too since you'll start getting mails with more accurate subject lines.
A word on empty subject line
Hiri doesn't let you send an email with an empty subject line. We do this for the same reason we put the subject at the bottom. We want you to write better subject lines. The recipient needs to be able to quickly decide what to do with your email, even without opening it. And a subject line with 'Untitled' or 'No subject' sure ain't gonna help them with that!