If you want to send bulk email blasts from a large list then definitely use a 3rd party, but it seems their emails were triggered programmatically from many different parts of their application. The email providers I have used don't make this easy so it is usually better to run the server yourself. You don't need much knowledge or experience to run an email server (if you are competent at general IT tasks already) but you need one thing: to actually check once in a while to see if your sever is sending email.
Which is the real problem here. Team members knew mail wasn't being delivered in the forums and they chose to ignore it. They must have never done any follow-up (personal email, phone call, survey) on new customers even when they were doing their big marketing "ramp-up." They must not have even checked with a test walk-through of the new user process. Leadership was just too far removed from the customer experience, whether they used a 3rd party email service or not.
It has been a few years since I have been saddled with email responsibilities so it's not surprising I am a little behind the times. But it still doesn't mean you shouldn't be checking that customers are receiving your emails.
I recently migrated a couple of my sites away from directly sending transactional email, to using MailChimp's Mandrill service. A few months later, I only wish I had done that sooner.
Which is the real problem here. Team members knew mail wasn't being delivered in the forums and they chose to ignore it. They must have never done any follow-up (personal email, phone call, survey) on new customers even when they were doing their big marketing "ramp-up." They must not have even checked with a test walk-through of the new user process. Leadership was just too far removed from the customer experience, whether they used a 3rd party email service or not.