"Failed to create outbound TLS connection. Message will be retried without TLS."
The Cisco PIX Firewall MailGuard feature interferes with this because the encryption interferes with its ability to inspect packets - it can't tell what danger might be included. Newer PIX versions allow you to make an exception for TLS, but with the older versions your only choice is to shut off the fixup (or have no TLS mail).
CISCO PIX Firewall.
Cisco's PIX firewalls implement a feature called MailGuard. When enabled this feature configures the firewall to run an SMTP proxy that intercepts SMTP requests. This SMTP proxy can cause problems with SMTP authentication.
The solution to this problem is to disable the mailguard feature for the
firewall. More information on configuring the firewall is available
Error '503 This mail server requires authentication': Article ME020135
How to configure the mail client when accessing MailEnable via POP and SMTP?: Article ME020198
|Product:||MailEnable (All Versions)|
|Keywords:||503 CISCO PIX authentication firewall unable to relay cant relay smtp|
|Class:||PRB: Product Problem or Issue|
|Created:||30/06/2003 8:56:00 PM|
|Revised:||Wednesday, May 4, 2016|