title: Mandrill: How long do I wait before assuming deliverability?
body: <p>I've set up a Mandrill webhook which will update my app whenever an email hard-bounces or is rejected, so I don't keep that particular email address in my database. The way it works is this: a user gives me an address, I send him a confirmation, and if I don't hear from Mandrill's webhook in 30 minutes, I assume it's OK.</p>
  
  <p>So I ran a some tests with non-existing addresses, and they didn't go too well. Most of them appeared as delivered for hours, long after I'd assumed they were fine.</p>
  
  <p>Also, I didn't account for the delay in receiving webhook batches. One mail bounced at 2:01pm, according to the outbound activity logs, but the webhook history shows a batch being sent only at 2:52pm.</p>
  
  <p>My questions is: how long should I delay my app's assumption of deliverability in order to give Mandrill enough time to detect hard-bounces / rejections and then send me webhook batches? I can live with letting some 5% bad emails going by because of delayed in processing on peak-time or other extraordinary events, but it seems like my 30 minutes isn't enough to catch anything at all...</p>