I'm working as a Network Administrator over a Decade in Datacenter and handled email marketing to server optimization over the years and currently provide Support, Setup, Configurations, Optimization and Maintenance for PowerMTA, Postfix, DNS, MailWizz, Ecommerce, Website ;)
Please find me your requirement, ie, number of emails per day, number of domains, audience type and geographic location so I can suggest you best ways to have your emails delivered to inbox.