Emails are things other people or companies or spammers send to you.
Posts on a forum are things you write.
I look at post count as one of the ways to measure how much I've had to say here, and since I started participating only relatively recently in the serial threads, most of those posts will still be viewable if one digs back far enough. My posts in the staff forum are no longer accessible to me, and I've permanently lost that post count.
There are forums where post count does matter, because higher post count means extra perks. The Star Trek forum I belong to has a batch of hidden forums, each of which is accessible only to members of a particular rank (post count = rank). For instance, Ensigns can't post in the Admirals' Lounge (and vice versa). I joined the Admiralty there last year, with a rank or two yet to go. At the rate I post, it'll take a few years since I'm not in the habit of spamming.
