I'm using fail2ban with CentOS 6.6. Something is causing fail2ban's alerts sent to root's mail to be rejected. Here's a clip from one of the error messages: Message 48: From MAILER-DAEMON at lion.protogeek.org Sun Dec 21 03:09:20 2014 Return-Path: <MAILER-DAEMON at lion.protogeek.org> Date: Sun, 21 Dec 2014 03:09:19 -0600 From: Mail Delivery Subsystem <MAILER-DAEMON at lion.protogeek.org> To: postmaster at lion.protogeek.org Content-Type: multipart/report; report-type=delivery-status; boundary="sBL97EKS003880.1419152959/lion.protogeek.org" Subject: Postmaster notify: see transcript for details Auto-Submitted: auto-generated (postmaster-notification) Status: R Part 1: The original message was received at Tue, 16 Dec 2014 03:09:17 -0600 from localhost with id sBG97E83025627 ----- The following addresses had permanent fatal errors ----- <fail2ban at example.com> ----- Transcript of session follows ----- <fail2ban at example.com>... Deferred: Connection timed out with example.com. Message could not be delivered for 5 days Message will be deleted from queue .......... I used to get the messages that are now being deleted after five days. Any suggestions? --Doc Savage Fairview Heights, IL