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:
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:
For other issues that might be caused by these features, please review the following article: http://www.symantec.com/docs/TECH85536