On Mon, 22 Jun 1998, Galen Hazelwood wrote:
> Exim is being inconsistent, but it _should_ be
> inconsistent. Messages received through SMTP are expected to be
> correct, and the sort of brain-damage-checking done on the command line
> is just a waste of resources.
I'm not sure I would use the word "inconsistent".
There are two different ways you can pass a message to Exim. One is via
SMTP. This is documented in the RFCs and is a standard protocol. The
message in the DATA section has to conform to RFC 822, in which there is
no mention of a "From " line. When expecting RFC822 header lines, if
Exim finds a line which is not in the correct format, it assumes it is
the start of the body. It would be within its rights to reject the
entire message, but I thought that the current action was more useful.
The other way of passing messages to Exim is via the command line, with
the message on the standard input. This is a private interface between
Exim and the program that calls it, so it can do anything it likes. In
practice, Exim tries to emulate Sendmail, because many UAs expect that
interface. After running Exim for a while, I discovered that Sendmail
and other MTAs do recognize "From " lines when called in this way, so I
altered Exim to do the same. Exim ignores such "From " lines if the
caller is not trusted, but if the caller is trusted, it takes the
envelope sender from the "From " line. The way in which it does this can
be tailored by some options whose names start uucp_ because incoming
mail from UUCP is one of the most common cases where this is seen. There
*is* an RFC which documents the "From " line as used by UUCP, but I know
of no documentation for its use as a mailbox separator. (This latter use
is really silly and causes a lot of problems, but we are stuck with it.)
--
Philip Hazel University Computing Service,
P.Hazel@??? New Museums Site, Cambridge CB2 3QG,
ph10@??? (sic) England. Phone: +44 1223 334714
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