The nice folks over at Postmark shared a new deliverability resource last week. The SMTP Field Manual. This is a collection of SMTP responses they’ve seen in the wild. This is a useful resource. They’re also collecting responses from other senders, meaning we can crowdsource a useful resource for email deliverability folks.
At least one ESP and Spamhaus are currently investigating bounce messages at a couple ISPs incorrectly pointing to Spamhaus as the reason for the block. The bounce messages are taking the form: smtp; 554 p3plibsmtp03-07.prod.phx3.secureserver.net bizsmtp IB105. Connection refused. 192.0.2.24 is listed on the Exploits Block List (XBL) <http://www.spamhaus.org/query/ip/192.0.2.24> Please visit http://www.spamhaus.org/xbl/ for more information. […]