http://www.rfc-editor.org/rfc/rfc2920.txt
RFC 2920: SMTP Service Extension for Command Pipelining, N. Freed2000-09-01T23:00:00-00:00This memo defines an extension to the Simple Mail Transfer Protocol (SMTP) service whereby a server can indicate the extent of its ability to accept multiple commands in a single Transmission Control Protocol (TCP) send operation. [STANDARDS-TRACK]