I think your are really missing something. First, Email-headers are
unordered
and every relay can, and probably will, rearrange them, add or delete
headers.
You therefore most definitely should not add any headers which are
position-dependent.
If you want to track mails somehow, add headers with timestamps.
This way you can watch the progression of an email without being
dependend on "sorted" headerlines.
This is incorrect, quoting directly from RFC 2822:
It is important to note that the header fields are not guaranteed
to
be in a particular order. They may appear in any order, and they
have been known to be reordered occasionally when transported over
the Internet. However, for the purposes of this standard, header
fields SHOULD NOT be reordered when a message is transported or
transformed. More importantly, the trace header fields and resent
header fields MUST NOT be reordered, and SHOULD be kept in blocks
prepended to the message. See sections 3.6.6 and 3.6.7 for more
information.
Trace header fields are not to be ordered, and should be prepended
when added to a message. Now that said I am not trying to track
anything, I simply want to prepend my additional headers onto the top
of the email, and seem to be unable to do that via the API, which I
think ought to be possible. If for example I was writing some kind of
an SMTP server with Python and needed to add said trace headers they
would need to be prepended, and currently cannot be (without doing it
by hand).
-David