@Jeremiah I'm not sure if I understand this right, but I would not be surprised if you can get along fine without paying for any special "transactional email" service.
If your MX goes to e.g. Fastmail, I think you can still send email from your own server somewhere if you add the other sending IP in the SPF record for your domain, thereby telling the world that legitimate emails can also come from that IP. Then you can send your emails yourself from your own server in whatever way you want.