The design of the site is very, very good. Within a couple of seconds I knew EXACTLY what this does. Not usually the case with a lot of startups out there. That text under the logo is very good. Having said that, unfortunately I'll join others in saying I won't use this. I'm one of hte "searchers" - my inbox is always full, but I search for right emails, instead of filing into folders and deleting.
A part of the problem here comes down not to the service you're providing, mtgentry, but what you're saying or not saying about it. So my feedback is about your customer-facing copy.
Although I love the clarity of the headline, I'd recommend you consider fleshing the headline out to address a key benefit or the single biggest point of value, possibly in a nicely sized subhead. Something like:
"Broadcast Your Inbox Health
When your team or family sees you're swamped, they'll only send you critical stuff."
A few other thoughts:
1. "Broadcast" is a scary word. It's clear and noticeable, but it's scary. Reconsider?
2. What's the pain you're eliminating? It's not making it so people are "less likely to email you", as you put it. We still need communication. It's just that, when we're busy, we don't want the emails we don't need. The pain you're eliminating is unnecessary emails. It seems obvious to me, but it's nowhere on the page. (Of course, I may be totally wrong!)
3. You write about what senders/recipients can see (i.e., "It allows anyone you email to see the size of your inbox"), but you don't write about what people can't see. That's important. The details that stay hidden from others - like subject lines and sender names - are even more important, in the sensitive world of personal and business comm, than what's shown to them. Tell potential customers exactly how private their inbox will remain.
4. People don't want others to know how jam-packed or empty their inboxes are because that says something about them. (Others have noted this already.) Assuming your product addresses this issue elegantly, you'll want to message this on your home page or in easy-to-read FAQs.
5. An 'ideal for' line would greatly help. People need to identify. Help them.
6. Why is Smoke Signal better than an auto-responder? Why is it better than IM statuses? Why is it more efficient or effective than the solutions the HN community is throwing out? A testimonial from a customer that covers off these sorts of things could do some serious heavy lifting here.
Sorry if that's going too far. It seems to me that there are a lot of great objections and anxieties rising to the surface in this thread. You can totally address them easily on the page.