A while back we launched our own RBL (*) called MXRBL, in response to customer complaints that we were doing a poor job of filtering spam. Since then we've been using this RBL to reject email from IP addresses that we have blacklisted as a result of customer complaints and log audits. Until today, there has been no way to receive mail from blacklisted IP addresses except by requesting that we delist the IP.
As of today, we are putting this back into our customer's hands. By default, email will be rejected for being blacklisted at MXRBL. However, you can now whitelist senders to opt them out of this when sending mail to you, if you wish to do so. You can find instructions on how to do that here: https://mxroutedocs.com/directadmin/spamfilters/
Do note that fully disabling all spam filtering on your account will result in it being re-enabled a few hours later. More about that here: https://mxroutedocs.com/presales/nospamfilter/