New SMTP transaction connections to Symantec Messaging Gateway may see a one to two second delay per connection when new non-local email addresses are encountered.
The delay, which was introduced in the 10.6 version of Symantec Messaging Gateway, is caused by internal processing of the non-local email addresses. This delay does not affect most transactions since the delay is typically minimal for new connections and multiple email deliveries are generally grouped to send more than one message per connection, which does not encounter this issue.
This issue is being investigated. Please subscribe to this article for updates.