To me, there is one big difference with postmark. Their focus is on transactional emails. Not marketing emails. I believe they have a separate service now for m

To me, there is one big difference with postmark. Their focus is on transactional emails. Not marketing emails. I believe they have a separate service now for marketing emails, but the big reason I chose them is that they are very focused on keeping their IP addresses clean. One way they do this is by only allowing users of their service to send transactional emails like invoices, password resets, or thing that have been specifically requested by users. I assume they keep all that on IP addresses reserved only for that. Most people won't mark a password reset email as spam. But they will frequently mark recurring marketing emails as such. I use Postmark for everything that is very important that it gets through. I actually use mailgun for mass emails, marketing, announcements, etc.