Yesterday firstname.lastname@example.org could send to me no issues
today email@example.com can not - they get an instant bounce back saying:
The following recipient(s) cannot be reached:
'DE' on 2/25/2011 7:56 AM
There was a SMTP communication problem with the recipient's email server. Please contact your system administrator.
<Exchange.abc.com #5.5.0 smtp;553 IP: 126.96.36.199 blocked due to very high Spam ratio!>
What would cause this - it seems like it is not even leaving their server.
They (firstname.lastname@example.org and the whole @abc.com domain) can send to any other address except my domain eg @gmail.com no issues.
They are not on a blacklist, I am not on a blacklist and their mail does not even hit my spam filter?