Since I turned on PBL blocking on my mail server (adding zen.spamhaus.org to the DNS blacklist), a few people have reported sending me emails, but I'm not getting them and they're not getting a rejection notice.

Looking through the logs, I can see that my mail server refused the email with a '554 Message contains known spam source in Received: header' (the header being the IP address of the sendee).

When I checked the IP address through spamhaus, it failed on PBL:

"It is the policy of Sky Broadband that email sent from this IP address should be sent out only via the dedicated outbound mail server for the Sky Broadband service."

Now I know the person who sent this email done so through their Yahoo on-line account, so are they saying that it's Sky's policy to block any emails unless it is sent through their mail server? Does this include email sent via HTTP?

I could add their block to my whitelist, but is there anything I'm missing here?

Thanks,

TEk