Virtual machine for a web application, it is still in testing.
reverse DNS is properly set up.
Postfix only listens on the local host.
Linux firewall drops anything not to port 80, 443, or a custom high
number port I use for SSH.
This postfix is not an open relay, or a relay for anything on the
Internet, it only exists so the web application can send e-mail.
SPF for the domain is correctly set up, DKIM for the host is correctly
set up, when it sends an e-mail and I inspect it - it passes the rDNS,
SPF, and DKIM checks.
So far it has only sent e-mails to addresses I control as the web
application is still in testing.
Yet yesterday the IP address ended up on Spamhaus blacklist.
I am 100% confident that no one else was sending e-mail from that IP
address, I'm a bit puzzled as to how the IP address got added to the
blacklist, but I was told that Spamhaus sometimes just adds an entire
subnet if more than one IP on the subnet was sending spam, and that's
probably what happened.
I think that is irresponsible of Spamhaus if that is what they are
doing, but is there something more I can do other than correct rDNS,
SPF, and DKIM to avoid getting on a blacklist?
