It seems to me that we are working with two different ideas of the
"end of mail data indication".
I would argue that it is a line containing only a period.
Others take the position that it is CRLF.CRLF
Those two are different, as someone writing a parser may discover.
The ambiguity between the two motivated my questions at the start of
this thread.
RFC 2821 does not seem to recognize the difference. Rather RFC 2821
confuses the issue. This sentence from section 4.1.1.4 can not be true:
"The mail data is terminated by a line containing only a period, that
is, the character sequence "<CRLF>.<CRLF>" (see section 4.5.2)."
because the character sequence "<CRLF>.<CRLF>" IS NOT a line
containing only a period. Mail data may be terminated by one or the
other but not both, because they are different and mutually exclusive.
We write "CRLF.CRLF" because that is an easy way to show that we
intend a line containing only a period. But CRLF.CRLF emphatically is
not a line containing only a period. A line -- one line -- cannot
contain two CRLF sequences.
Rich