Rackspace

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

Delivering to
There is very little information available  about delivering to domains hosted by Rackspace.

Postmaster pages
Rackspace postmaster is operated on the white label https://emailsrvr.com/ service.

Feedback loop
Rackspace does provide a FBL administered by Return Path. Applications are accepted at the Rackspace FBL signup page.

Whitelist
Rackspace does not offer a whitelist for senders.

Certification Services
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.

Support for Senders
postmaster@emailsrvr.com

Known spamfilters
Rackspace has not published any information about commercial spamfilters they may use.