Got a bit of a weird problem here with Postfix.
Been getting a whole bunch of notices where fail2ban has banned 69.164.196.21 (ryujin.darkdna.net) for failures against Postfix.
Here is a relevant snippet from Postfix's log:
Jan 13 17:56:26 postfix/smtpd[14563]: connect from ryujin.darkdna.net[69.164.196.21]
Jan 13 17:56:26 postfix/smtpd[14563]: NOQUEUE: reject: RCPT from ryujin.darkdna.net[69.164.196.21]: 554 5.7.1 Service unavailable; Client host [69.164.196.21] blocked using b.barracudanetworks.org; from=<discuss-owner@lists.opennicproject.org> to=<******> proto=ESMTP helo=<ryujin.darkdna.net>
Jan 13 17:56:27 postfix/smtpd[14563]: disconnect from ryujin.darkdna.net[69.164.196.21]
This happens about 4-5 times per day, depending on how much mail gets sent from that maillist.
Now, I get and see that Postfix blocks it as a result of a match against the b.barracudanetworks.org blacklist.
What I don't get is why. As far as I can see from two blacklist checkers (mxtoolbox.org and anti-abuse.org) neither the IP 69.164.196.21 nor the hostname ryujin.darkdna.net is actually listed. (For what it's worth, the host/IP in question seems to be one of Linode's).
This isn't the only host it's blocked. Postfix has apparently been doing this for a while now, blocking hosts it thinks is in the barracudanetworks blacklist when they aren't.
I can access their blacklist just fine from my computers, after following their testing instructions.
I'm stumped, and would appreciate some help or pointers on where to look!
