PostPath: Have you ever heard of these guys?

by Volker Weber

PostPath claims to have "the only Exchange Server alternative to deliver drop-in Microsoft interoperability across the email ecosystem." How does that work? They have reverse-engineered the protocol and make the management console, the other servers and the clients believe they are talking to real a Exchange server. They deliver the experience from a Linux machine, which they claim has a lot of advantages over an Exchange server, for instance in the backup space.

I see at least two problems:

More >


One huge bit of reverse-engineering of a Microsoft protocol was done by Andrew Tridgell for Samba. The protocol underwent changes to which the Samba team had to adjust. I don't think either he nor the Samba project were ever sued, but of course that may be because they didn't create a commercial product.

Jan-Piet Mens, 2007-08-29

dont they do the same as Zimbra ?.

the main problem with clones are that every single 3rd party vendor will run away screaming from it until they reach a critical mass.

i havent seen a single Zimbra or Postpath server here or heard about it for that sake.

Flemming Riis, 2007-08-29

One of the projects I manage here at Microsoft is a licensing program for the Exchange/Outlook transport protocol (I manage the technical aspect, not the legal or licensing aspects, of course, so be kind, Notes folks!). We have documented and made available all RPC wire traffic (all properties, ROPs, etc.) between Exchange & Outlook from versions 2000 through 2007. It allows an alternate client to communicate with Exchange the same way that Outlook does or an alternate server to communicate with Outlook the same way the Exchange does. At least one of our clients is implementing this on non-Windows hardware.

This program was announced in January, 2007.

Here's the details --> Exchange Direct Connect.

Amy Blumenfield, 2007-08-30

Thanks, Amy. Much appreciated.

Flemming, completely different animal. Like most of the other contendors, Zimbra needs a desktop connector. It converty what Outlook says to what the Zimbra server wants to hear. Over the wire, it speaks the Zimbra protocols.

With PostPath the server pretends to be Exchange. No desktop installations necessary.

Volker Weber, 2007-08-30

Volker, oh was told that it was native also a while back and never bother to look into it.

Flemming Riis, 2007-08-30

I have been using PostPath for several months now. During my evaluation, I asked similar questions to what you have written and learned the following:

* Microsoft could change the protocol as they wish and without prior notice.

It is unlikely that Microsoft drastically changes the protocols to prevent the PostPath server from communicating with Outlook and Exchange because that would break interoperability between all the other components of this ecosystem including between Exchange servers, and between Exchange and Outlook.
Microsoft do extend their protocols from time to time. In that case, they provide automatic fallback to older protocol versions where new features are unsupported, to avoid breaking backwards compatibility with their own products. PostPath can always choose to add those new protocol extensions, and can even choose to do so working off Beta Microsoft products if a feature is of sufficient interest.

* Microsoft could probably sue them for a number of reasons.

Not really. The right to inter-operate in this fashion is well protected in both U.S. and International law, and what PostPath is doing is inter-operating with other (Microsoft) products that customers have, like Outlook, Active Directory, and previously-deployed Exchange servers. I understand that PostPath also has policies to ensure its implementation is clean, for instance it won’t hire any ex-Microsoft engineers.

In any case, the Samba example also uses protocol analysis and re-implementation. Being an open source project, they may not have such strict policies as PostPath, but still there has never been a sign of lawsuit from Microsoft.

* Zimbra

Zimbra is a very different product. It is a great product but it does require a plug-in on every desktop and laptop in order to work with Outlook. It also is not using AD directly and can not co-exist natively with other Exchange servers. Compare migrating 100s or 1000s of users over to Zimbra at once rather than gradually migrating them to PostPath. With PostPath, you would not even need to tell the user that their mailbox was moved from Exchange. Even shared calendaring and free/busy continue to work with the users that is still on Exchange. Global address book is still available... For most corporates, interoperability and coexistence are key – and by the way, most of Zimbra’s customers seem to be outside of the corporate world.

I hope this helps.

Max Winkler, 2007-09-11

Old archive pages

I explain difficult concepts in simple ways. For free, and for money. Clue procurement and bullshit detection.


Paypal vowe