XMS Virtual MTA technology allows you to send different classes of email using unlimited unique IP addresses on the same MTA server. This feature can be used to control the routing of different classes of email deliveries such as transactional messages from newsletters or marketing emails. Thus if your marketing email is blocked your transactional email will not suffer the same fate. You can specify a set of IP addresses and custom header combinations to use when sending a message to a specific domain.
Your IP address is like your fingerprint in the email sending process. Careful management of IP addresses will result in a lower probability that any one or, a set of emails, will be blocked due to a blocked IP address.