Exchange Proxy Anyone?

At UDS, there was talk (mostly from Dan Shearer) about using Openchange to provide a mapi proxy to MS Exchange.  I find this interesting.  If Dovecot/Postfix could use it, it would allow *NIX clients to talk to Exchange without turning on OWA.  This would delight sys admins on both sides of the fence.  Of course, Outlook clients could also talk straight mapi to the proxy as well.

I like the idea of abstracting MS Exchange, because once we have all the clients talking to us instead of MS Exchange, it makes it much easier to replace exchange.

The Openchange folks have made an announcement.

9 Responses to “Exchange Proxy Anyone?”

  1. 1 Vadim P. May 29, 2008 at 4:17 pm

    Your planet ubuntu title is broken, it just leads back to the planet… I clicked on it like 3 times while multi-tasking, then realized this 😦

  2. 2 dendrobates May 29, 2008 at 4:19 pm

    I am aware of the problem, and I am trying to figure out why.

  3. 3 Josef Assad May 29, 2008 at 4:31 pm

    MAPI/RPC is proprietary. fetchExc has always doneme well,but it’s probably pretty far from what you have in mind.

  4. 4 imbrandon May 29, 2008 at 5:48 pm


    try using the atom feed for planet instead of the rss one, it should fix the title problem.

  5. 5 dendrobates May 29, 2008 at 6:36 pm


    Thanks, that solved all my problems.

  6. 6 Dan Shearer May 29, 2008 at 10:18 pm

    Hey there Rick,

    The architecture I think you’re asking for could be called an Exchange wrapping service. And the nice thing about it is that no open source software needs to be harmed in order to deliver it (hacking Exchange knowledge into Dovecot, Postfix, Exim… scary!) Your arhitecture is good and the result will be a more predictable and controllable groupware infrastructure without causing disruption.

    From what you say there are two things you’re looking for:

    1. No RFC-compliant ports of Exchange are to be exposed. In other words, if a client of any kind connects to Exchange using IMAP, POP (or potentially CALDAV and WebDAV) then they connect to well-known piece of OSS that then relays the data to Exchange over MAPI. Meaning you never talk Microsoft’s version of IETF protocols, or expose them on the Internet. For Postfix (and Exim and any other MTA) we write a small “local delivery agent” that functions very largely like the shipping openchangeclient, built on libmapi. The MTA just thinks its procmail or maildrop. For Dovecot or anything else that uses Maildirs we again use the libmapi client library, this time to construct a filesystem that exposes the Exchange mailboxes as Maildirs. All of this is MAPI client functionality, see . So there is work to do, but not a lot, and thankfully not butchering respected bits of OSS!

    2. No MAPI ports of Exchange are to be exposed when talking to MAPI clients. In other words, Microsoft Outlook talking to Microsoft Exchange has to go through a MAPI-to-MAPI proxy. This gives control over the conversation in a lot of ways. This is what you get from the link you gave ( ) without any extra work.


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