HN turned me on to Postmark for transactional emailing and I haven't looked back since then. So, I'm curious to know what the best Email Service Providers are for marketing email campaigns in terms of deliverability.<p>I have experience using:<p>* MailChimp
* Constant Contact
* Hubspot
* Autopilot<p>and I haven't really found one that gets it right as far as B2B deliverability goes.