Symantec Messaging Gateway (SMG) fails to deliver messages and increases the amount of messages in the Delivery queue.
450 4.4.1 [internal] Connection Timed Out
This message indicates that the connection is either timing out or being interrupted while the message is being transferred to its destination which can be a local message or a non-local message.
This issue might be due to the Delivery Bindings configuration:
Login to the Control Center web interface.
Navigate to Administration -> Hosts: Configuration.
Edit the scanner that is having this issue.
Click on the SMTP tab.
Click on the Advanced Settings button towards the bottom of the page.
Click on the Delivery tab.
Under "SMTP Delivery Bindings" towards the bottom, change the bindings for non-local and dynamically routed messages to "Auto".
If you have a firewall between the Symantec Messaging Gateway and the destination SMTP server, which can be a local or non-local mailbox server, make sure SMTP/ESMTP features are disabled. Consult with the firewall vendor for information on how to disable these features.
Firewalls that are known to have such features are:
Cisco ASA - Disable all esmtp_inspect features
Cisco Pix - Disable mailguard
Checkpoint - Disable the smart defense technology for SMTP/ESMTP