SMTP Notification
Connect:Direct® uses the SMTP notification method and exchanges e-mail using TCP/IP and a message transfer agent (MTA).
The SMTP standard is one of the most widely used upper layer protocols in the Internet Protocol stack. This protocol defines how to transmit messages (mail) between two users. SMTP uses spooling to allow mail to be sent from a local application to the SMTP application, which stores the mail in some device or memory. Once the mail has arrived at the spool, it is queued. A server checks to see if any messages are available and then attempts to deliver them. If the user is not available for delivery, the server tries later. Eventually, if the mail cannot be delivered, it will be discarded or returned to the sender.