dealing with Microsoft Exchange, when you really want to use SMTP

Thursday, 9 December 2010 | Brad Hards

I've been doing some work on <a href="http://www.openchange.org>OpenChange, including parsing RFC2822 format messages into Exchange RPC properties. One of the test tools I have can parse up some kinds of RFC2822 / MIME messages (plain text, HTML, some mime/alternative and text/calendar) and upload the results to a Microsoft Exchange server as a particular user.

With a little bit of unix-style tool combination, you can plug this into something like Postfix. So if you're in a situation where you want to integrate a tool that wants to send mail via SMTP, but your network is pretty much "Exchange." (and you can't send SMTP directly), then this might be useful.

When using Postfix, you'd add a transport entry, either a wildcard:

* oc:localhost

or a restricted list if you like.

Enable the transport mapping in main.cf:

transport_maps = hash:/etc/postfix/transport

Then add an entry to master.cf to match the required transport:

oc	unix	-	n	n	-	1	pipe
   flags= user=bradh argv=/path/to/script.sh

where the script receives the mail, and invokes the oxcmail_test application:

#!/bin/sh

SCRIPT_TMP_DIR=/var/spool/myscript
OC_SEND="/home/bradh/openchange/branches/oxcmail/liboxcmail/test/oxcmail_test --dump-data -d9 --database=/home/bradh/.openchange/profiles.ldb"

# you could also choose to remove $SCRIPT_TMP_DIR/oc_send.$$.log if you don't need the records
trap "rm -f $SCRIPT_TMP_DIR/$$.msg" 0 1 2 3 15

cat > $SCRIPT_TMP_DIR/$$.msg

$OC_SEND $SCRIPT_TMP_DIR/$$.msg > $SCRIPT_TMP_DIR/oc_send.$$.log

exit $?

I would caution that the code is pretty experimental - its still in a branch for a reason! However I would appreciate some external testers if you're feeling particularly brave, and have the right kind of environment for testing this. You can pick up the code from svn (http://svnmirror.openchange.org/openchange/branches/oxcmail) and build it using the instructions on the OpenChange wiki. In addition, note that you can't usually set the From address, so you'll probably be restricted to sending from one pre-configured user (or perhaps a small set of users)

If you have any questions, try to catch me on IRC (#openchange on freenode), leave blog comments or use the devel mailing list.

Future plans involve a sendmail-like application for those applications that want to sendmail instead of SMTP. Hopefully that will allow me to send from KMail without needing to go via the SMTP path.