We also host our own email and need to move to using our own AS and IP space to avoid being negatively impacted by spam sent by other customers in the same IPv4 /24 or even the same AS. Providers offering VPS instances generally have terrible IP reputation especially for IP space they use for floating IPs but the instance IPs have bad reputation too. A floating IP is needed to avoid losing positive IP reputation and work done to undo inclusion in blocklists for an email IP though.