Quality service and plugin

I have used SendGrid, MailJet and MailGun.
PostMark blows them out of the water so far on a few fronts.

1. IP addresses aren’t getting blacklisted as it only allows transactional mail.
2. You can send from different domains/emails on the one website as long as they’re added to your PM account.
3. Support is great!

If you’re just needing transactional email, PM blows them away!