Why is Optus blocking all email from my domain?


Every email sent to an optus user from my domain comes back with this:

 521 5.7.1 <>: Recipient address rejected:
    You are not allowed to send mail. Please see 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.



Re: Why is Optus blocking all email from my domain?


Hey Brian,


It appears that the IP address your site is hosted on ( / 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:


Let us know how you go.



I’m a Yes Crowd Champion (not an Optus employee). I share my knowledge on Yes Crowd on a voluntary basis. If I answered your question, please mark it as a Accepted Solution. If I helped you out, hit that Kudos button Smiley Happy

Re: Why is Optus blocking all email from my domain?

[ Edited ]


I tried resetting CloudMark yesterday but it made no difference.  I checked yesterday (see 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 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.




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