GO!NotifyLink Enterprise Server:

The Response Handler service is responsible for handling all device commands from the device.  Older data devices will send commands via SMTP back into the gateway mailbox account.  The ResponseMailClient service will find these messages and place them into the PendingResponses table. 

High speed devices will send replies back via the web, where a send.asp page will handle the messages and place them into the same PendingResponses table.  The service will then pull messages from the PendingResponses table to be processed.  Successful messages are deleted from the queue, while messages that fail are retried every 5 minutes, up to a maximum of 30 minutes.  If they do timeout you will receive a message in you Administrator's Email Account that was setup under NotifyLink. PIM responses are ignored and moved directly to the PIMResponseQueue.