Unfortunately, we have a long list of proposed new services, but at the moment we are focused on ensuring that the services we do host are done properly and are fully supported (e.g. we are currently working on upgrading our hundreds of mailman2 lists to mailman3 - which is our priority over adding a new newsletter service). It’s a bummer because I really like some of the new newsletter sites, especially ghost.
Aside from the mailgun limitation, ghost is at least run via node, which means in theory it could be hosted on our shared infrastructure without out intervention. I’m not sure about Keila (which seems to be written in elexir - I’m not sure anyone has tried to run an elexir app!!).
As for bulk email - yes, it’s a real challenge - something we have been working on for 20 years. And, although no bulk mail provider is perfect, we do fairly well and send a lot of email. These are our stats from the last 7 days:
Part of our success recently is that most of the big players, like Gmail, seem to be using DKIM to rate senders based on their domain rather than the sending IP address. That doesn’t mean we don’t get blocked from time to time (yes, I’m looking at you Yahoo…), but email reputation seems to be increasingly based on the domain of the from address.
As for the unauthenticated smtp - we don’t in fact support unauthenticated smtp - that would be a nightmare. Instead, we authenticate by IP - you can only relay if you are coming from one of our IP addresses. And… that will be changing soon (note above about how we are working on tightening up our existing services before launching new ones!!).