On 2 Dec 2015, at 10:42, Bryan K. Walton wrote:
We've got a postfix mail server running postscreen that is configured
to make use of the postscreen_dnsbl_whitelist_threshold feature. The
postfix version is 3.0.3. Things have been working really well for
the last 6 months, or so. However, we have recently discovered an
issue where it seems that incoming email that comes from
*.outbound.protection.outlook.com servers seem to not be handled
properly.
[...]
Questions:
1. Why is this message getting a 450 message? Is the outlook mail
server speaking out of turn here?
Since you didn't bother providing 'postconf -n' output, which would
provide useful clues, we are left with making random guesses...
My random guess: you're doing sender verification. Don't. It's broken in
concept and especially broken operationally if you want to communicate
with people using MS products.
