Assuming it has an API, I would prefer to use this over a service such as Mailgun. We used to have our own mail server, but without an easy API to get deliverability details per mail, we ended up switching to Mailgun. Since the switch, our deliverability has nosedived (we're currently not paying for a dedicated IP though) and mails are constantly bouncing due to the low reputation of Mailgun's shared IPs.

Mailgun's 30-day retention period is also a bit absurd, since most of our clients require mail audit trails in the region of 6-12 months.