Right now we're using AWS SES for our MTA. We've had a pretty great experience with them to date. We don't currently offer dedicated IPs but we likely will in the future. When we do, we want to make sure that customers have the required send volume to actually see a benefit from using one. I think a lot of services offer dedicated IPs too early as a panacea for increasing delivery rates. What we've noticed is that these initial IPs are warmed up so perform well, but over time, if the send volume is too low, it's reputation can atrophy.

We monitor our delivery platform wide and proactively contact customers if there are issues with their account.

As far as spam, yes, we allow you to contact within your own audience as much as you like but we do monitor this for abuse.