Question
What is PIPELINING and what advantages does this enhanced feature offer?
Answer
The pipelining command is an extension of SMTP. It reduces the time it takes to send multiple messages. A sending server would use pipelining to send all the messages it has to a receiver in one go.
This command is not available for mail servers that do not support Enhanced SMTP.
Using the standard SMTP protocol, the RSET command is issued to clear the buffers that stores whom a mail message is from, who it is going to and the actual body of the message.
It simply sends all the commands “down the pipe” without waiting for a response from the remote server. Once all the commands have been received, only then will the remote server issue all its responses at once.
The advantage to this method in comparison to SMTP’s RSET is that pipelining uses just a single thread irrespective if there are multiple recipients. Thus the actual body of the message is transmitted once.
Keywords:esmtp pipelining extension enhancement