Our customers using the SMTP relay can now add a full class C IP block to their list of authenticated IP addresses, instead of adding single IPs at a time. To add a class C block of IP addresses (255 IP addresses), contact our support team, and they can do this for you, as the feature is not yet available through our web interface.
Why would I need to allow 255 IP addresses to relay email?
Most customers will not need to do this, but we have some customers that are ISPs, web hosting companies, and cloud computing services. These organizations often need to allow larger blocks of IP addresses in order to serve their own customers.