-oem
====

This document explains what I found out about the -oem/-oee options. It
is intended as a knowledge base for further development on this topic.
In version 0.3.0 (2010-11), masqmail's implementation of -oem is
considered broken and -oee is not implemented.

Following is the behavior masqmail actually had:

    If -oi/-i is given, -oem is ignored.
    If no -oi/-i is given, always return with a non-zero return code.

This current behavior is not like it should be.


The desired behavior
--------------------

It had been difficult to identify good explanations.  The problem, as
often, is that sendmail's source would be the definitive definition.
But in which version and what if common behavior differs from sendmail's
(maybe as a result of misunderstanding)?  Exim's documentation has proven
to be a valuable resource.

In exim the behavior is such:

    If an error is detected while a non-SMTP message is being received
    (for example, a malformed address), the error is reported to
    the sender in a mail message.  Exim exits with a non-zero return
    code then, no matter if the error message was successful or not.
    (In exim, -oee is similar but exim returns successful if the error
    message had been sent successful.)

The mutt wiki writes about ``sendmail -oi -oem'':

    The mail server (in this case sendmail) will receive the message
    in input, and will parse it. In case of a malformed message,
    it will send an error message to the user to whom belongs the
    MUA trasmitting the message (e.g. user@localhost.localdomain),
    and it will exit with a non zero exit code: the -oem flag forces
    the returning of a non zero exit code even in the case the error
    message has been successfully sent to the local server.


What does it mean for masqmail?
-------------------------------

Masqmail does not send error messages on malformed addresses.  It does
not much check for syntax.  It detects general errors (unexpected EOF,
no recipients, max message size exceeded) (see masqmail.c:mode_accept())
but simply prints a message to stderr and exits non-zero.  I think that
currently it is not of need to add some elaborate error handling in
this area.  Hence, for the implementing of -oem and -oee would do assume
that sending the error message does always fail (because we never send
any such message) and hence we exit non-zero on error.  This is the
similar behavior of both options.

From 0.3.1 on masqmail will not recognize -oem anymore and thus ignore
it like any unknown -oXXX option. It's behavior is then as if error
message sending fails.

Remind that all this affects only the case of accepting non-SMTP messages
on stdin.


On the relationship of -oi and -oem
-----------------------------------

It seems as if the two options should not affect each other; in contrast
to the behavior in masqmail before 0.3.1.  Their relationship is just
that -oem does only affect non-SMTP messages on stdin, which is the
typical use case of -oi.


meillo