In the past 3 days we have 5 domains to which we can no longer send emails. WE receive a 554 error generally indicating the requested server is refusiing the email at the greeting. I have contacted the companies rejecting the emails and one has ressponded we are on a blacklist. I checked using MXTOOLBOX and our IP address is not listed on any public blacklists. I was eventually directed to a site (openrbl.org) and it indicates our doamin is blackilisted by apnews_l1. From what I can gather this is a private blacklist (appears to be out of Germany) site that is asking for money to be removed from the list or wait 7 days and the domain will be removed at that time. We are not spamming, how we got on the list in the first place puzzles me. I have never seen a site asking for money to be removed from from a list. Has anyone come across this before? Is this common? Are there any other options?
What stops sites like this from putting you back on the list after being removed from it?