FYI, the sites mailserver is listed on sorbs, which causes blocking on many mailservers including my own.
postfix/smtpd[24408]: NOQUEUE: reject: RCPT from mail-qk0-f193.google.com[209.85.220.193]: 554 5.7.1 Service unavailable; Client host [209.85.220.193] blocked using dnsbl.sorbs.net; Currently Sending Spam See: http://www.sorbs.net/lookup.shtml?209.85.220.193; from=<[email protected]> to=<xxx> proto=ESMTP helo=<mail-qk0-f193.google.com>
Interesting, the forum uses Google Apps as the SMTP provider for email so I guess Google has been blocked. All emails shouldn't come from the same IP but I could see that being a problem in general.
Two of the most well known are listed below:
Dynamic User and Host List (DUHL): This list is intended to contain IP addresses that ISPs assign dynamically.
Spam list: This list contains IP addresses which SORBS believe are or have previously been used to send or relay spam