You have to request this feature sending an email to [email protected] and after an approval workflow you will be enabled to use one of the following server as mx depending on the datacenter where you are established
Once routed throgh the service you can configure something about email blackslist and whitelist on your admin panel:
Manage Organization -> System Settings -> IBM SmartCloud Notes -> Account Settings
On Email filters you can set the Black List / White list for all domains and some other setting like "Report as spam" or Junk mail report.
Another info to know is there is possible the inbound blacklist management through this link where you can ask about ip address removal .
Here the technote about viewing or removing IP address from the list dnsbl.cobion.com list.