Every email sent to an optus user from my domain comes back with this:
521 5.7.1 <email@example.com>: Recipient address rejected: You are not allowed to send mail. Please see http://csi.cloudmark.com/reset-request/?ip=184.108.40.206 if you feel this is in error.
This has been happening for a few days. I have checked CSI Cloudmark and the reputation seems OK. Neither Hotmail nor Gmail are blocking.
Pretty poor form for Optus customers who have subscribed to receive mail and have it blocked by a faulty system.
It appears that the IP address your site is hosted on (220.127.116.11 / westgatebaptist.org.au) has been blocked by CSI as confirmed in the message you received.
Could you point me towards where you have checked that this IP address's reputation is "OK"? I'm seeing otherwise.
I would recommend you submit this form to have your IP reviewed: http://csi.cloudmark.com/reset-request/?ip=18.104.22.168
Let us know how you go.
I tried resetting CloudMark yesterday but it made no difference. I checked yesterday (see anti-abuse.org comment below) and it said that the domain had been listed, however was no longer. I think the listing had stopped 3-4 days ago. No information is given anywhere I can find about why it has become listed. If I could see that other domains from the same host were spamming I could challenge the ISP, but I can't. I know that the same mail message is going to gmail, hotmail and a number of other mail services without challenge. So whatever Optus are using isn't common.
I have looked on MXTools, Barracuda and a number of other sites that don't even report on Cloudmark. No other list on those sites has this domain listed. I did find aniti-abuse.org that would look up CloudMark. It lists 55 lists including Cloudmark which do not have it listed. So this is what I am referring to when I say that I can't see it listed.
If you are seeing otherwise it would be really helpful for you to share where you look.
The domain is setup with spf and DMARC which have been enough for Gmail and Hotmail to be kind to us.