1. Add your domains in SpamExperts, please refer to https://cloud.readyspace.com/knowledgebase/article/191/how-to-add-domain-in-spamexpert/
2. Add new/edit your current MX and TXT record for your domains according to the followings:
-MX record: mxcluster.cleverspeed.com
-v=spf1 ip4:YOUR IP ADDRESS a mx a:spf.cleverspeed.com -all (replacing YOUR IP ADDRESS with your server IP)
If you are using ReadySpace nameserver, please refer to https://cloud.readyspace.com/knowledgebase/article/228/manage-dns-record-in-dns-hosting/ for editing DNS records