Fired while the message text gets transferred to MailServer .
One or more Transfer events are fired during message delivery. Messages consist of MessageText and an optional AttachedFile. The BytesTransferred parameter shows the number of bytes sent starting from the beginning of MessageText and/or AttachedFile.
The Direction parameter shows whether the client (0) or the server (1) is sending the data.
The PercentDone parameter shows the progress of the transfer in the corresponding direction. If PercentDone can not be calculated the value will be -1.
Note that events are not re-entrant. Performing time consuming operations within this event will prevent it from firing again in a timely manner and may impact overall performance.