However, before that, validate the sending domain via DNS.
Our infrastructure is world class with almost to 100% uptime. We use geo-distributed high capacity load balanced incoming SMTP Gateways where the email does not even touch the disk (in the memory storage).
The email can be routed based on sender, recipient, tags or users activity (e.g.: active users get to use one pool and inactive users get to use another pool).
Of course, we offer a REST API, SwiftMailer plug in play transport, detailed reports and the most amazing transactional email templating features.