Why does the ESA accept and deliver mail messages containing bare <LF> characters?
SMTP commands and message data are transmitted in "lines". Lines consist of zero or more data characters terminated by a <CR> character followed immediately by a <LF> character. This sequence is denoted using the string <CRLF>. RFC2821 requires SMTP clients and servers to not accept any other character (such as a "bare" <LF>) or to generate any other sequence as a line terminator.
The MTA component of the ESA accepts and delivers messages that include bare <LF> characters as line delimiters, in the interest of better interoperability and in response to overwhelming customer requests. ESA users have the choice to pass bare <LF> or <CR> line delimiters through or to "clean" these delimiters, replacing the single characters with the complete <CRLF>.