Rackspace Email & Apps is the mail hosting arm of Rackspace Managed Hosting
The Email & Apps division of Rackspace was formerly known as Mailtrust and was formerly a separate company named Webmail.us
There is very little information available about delivering to domains hosted by Rackspace.
Rackspace postmaster is operated on the white label emailsrvr.com service.
Rackspace does provide a FBL administered by Return Path. Applications are accepted at the Rackspace FBL signup page.
Rackspace does not offer a whitelist for senders.
Rackspace uses the Return Path Certified whitelist in mail delivery decisions. Mail from IPs on the Return Path Certified list will see better delivery at Rackspace domains.
Rackspace provides delivery support through email to email@example.com.
Rackspace has not published any information about commercial spamfilters they may use. They do run an internal blocklist called blagr.emailsvr.com, which does include IPs from some third-party sources.