Do you do any edits for previous days? Seems like it would be difficult with email.

No. But editing a handwritten journal would hardly be any easier. It's a matter of what features you care about, I guess. I have never needed to edit past entries - that would be historical revisionism. It's not a feature I personally need for my journal. If I cared about that for some reason, I suppose I might use a different method.

If I realize I forgot something from yesterday, I just add it the next day.

You could theoretically reply to a previously sent letter from either your main or "journal" email to "update" an entry.