Some users may have had mails bounce recently with an error referring to a blacklist called ips.backscatterer.org, or no clear error at all. This is caused by the sole blacklist runbox’ mailserver IP address is on, which is a list which only blacklists mail servers for handling mail bounces in certain ways. Many other mail servers does it in the same way we do, but our large volume and problems with the IMAP bandwidth quota (now solved) have probably caused us to be on this list on and off for years.
This is NOT a spammer blacklist in other words, and it is irresponsible and uninformed to bounce mails based on any single IP blacklist, but especially this one. And recently, it seems that far more services use this list in such a manner. If your mails have bounced from a domain where you have contacts, we recommend sending them the following link:
http://www.backscatterer.org/?target=usage
We may become delisted as of Oct 12, and will update this post then if so.
UPDATE: We are currently delisted, but will update this post if we are re-listed.