I am often asked whcih blocklist providers do I use / trust not to get mail filtered becouse of bad blacklist provider.
On my servers I am using three lists (sorted by quality – my personal opinion 🙂 ):
I use this three lists without getting in troubles – at least for now. I suggest that you regularly check your SMTP logs to see how list are working.
I always notify sender that it was blocked by a blacklist.
Here is an example from and Exchange 2007 SMTP recieve log:
> “220 mail.mydomain.com Microsoft ESMTP MAIL Service ready”
< EHLO [18.104.22.168],
> 250-mail.mydomain.com Hello [22.214.171.124],
< MAIL FROM:<cathiFerm@flagpeakproperties.com> SIZE=656,
> 250 2.1.0 Sender OK,
< RCPT TO:<firstname.lastname@example.org>,
> 550 5.7.1 Your IP is blacklisted. http://www.spamhaus.org,
> 221 2.0.0 Service closing transmission channel