MS-Exchange Compatibility

Q: Is there a Linux client for Microsoft Exchange Server e-mail and scheduling?

A: There are a variety of solutions to this problem. None are yet quite as straight-forward as one might hope, because of obstacles posed by the system's highly proprietary nature. 100% open-source solutions are not yet available (see remarks at end), but are coming along rapidly.

Some possible solutions:

1. Use Bynari's Insight (http://www.bynari.net/), a proprietary-software Unix client for MS-Exchange, fully compatble with MS-Outlook and reporting supporting all of its functionality, natively.

Bynari's earlier TradeXCH can also fit this need, operating in either of two modes: (a) Use it as a generic IMAP/SMTP client, as described in the next option down, with functionality disadvantages, accordingly. This mode requires that Exchange Server's IMAP Connector and SMTP Connector be installed on the Microsoft Windows NT mail server. (b) Install Bynari's Peermail Access Service (PMAS) on the Microsoft Windows NT mail server. This mode permits TradeXCH to support the full range of MS-Outlook/Exchange features (e-mail, calendars, meeting-scheduling), and thus achieves integration comparable to that of the MS-Outlook client on Win32.

Bynari has an Exchange Replacement HOWTO whitepaper, here: http://www.bynari.net/whitepapers_howto.html

2. Install Exchange Server's IMAP Connector and SMTP Connector. (This also provides X.400 address support on the server end.) You can then send and retrieve mail from any Linux e-mail client that supports IMAP, including Netscape Mail. This solution does not give calendar access, or access to some advanced e-mail forwarding and "groupware" features.

3. Install Exchange Server's POP Connector and SMTP Connector. You can then send and retrieve mail from any Linux e-mail client that supports POP3, including Netscape Mail. This solution does not give calendar access, or access to some advanced e-mail forwarding and "groupware" features.

4. Run MS-Windows 9x's Exchange Client on your Linux system under VMware (http://www.vmware.com/) or Win4Lin (http://www.netraverse.com/). (Both are proprietary packages.) This gives robust access to all Exchange e-mail and calendar features, at some cost in system overhead to run VMware/Win4Lin, plus the cost of a copy of MS-Windows 9x and VMware or Win4Lin.

5. Run MS-Windows 9x's Exchange Client on your Linux system under WINE (http://www.winehq.com/). (WINE is open-source.) At a minimum, MS-Exchange Client v. 5.0 is reported to have tested OK under WINE. Later versions can at least be tried, with no cost other than time and trouble.

6. Install Exchange Server's SMTP Connector, and then run an SMTP MTA such as Sendmail on your Linux box. The Linux box and the Exchange server can then communicate as SMTP peers. (You may find it desirable to perform header rewriting on interchanged mail, to better integrate your company's mail hierarchy.) This solution does not give calendar access, or access to some advanced e-mail forwarding and "groupware" features.

7. Enable Exchange Server's Webmail component (in Exchange Server 5.5 and later), and use a Web browser on Linux. Again, you may lose access to some advanced Exchange features. (Addendum: Reportedly, this approach does not work because Microsoft has ensured that Webmail works only with Microsoft Internet Explorer on the client end.)

8. Install Infinite.com's proprietary WebMail Server (http://www.ihub.com/ - not to be confused with Microsoft's Exchange Server Webmail component) on a Win32 machine that can connect to the Microsoft Exchange Server machine. You must also install WebMail interface software on the Microsoft Exchange Server machine, itself. This gives users with Web browsers on any platform access to Exchange e-mail and calendar information. It's unclear what access to other Exchange groupware features is possible.

9. Install MS-Windows Terminal Server + Citrix MetaFrame on your MS-Windows NT server, and run Citrix's ICA client for Linux. (All of this is proprietary-licensed software.) This gives robust access to all Exchange e-mail and calendar features, as you are running Microsoft's Exchange Client on your NT server remotely.

10. Switch from MS-Exchange Server to Sun Microsystems's iPlanet Messaging Server (successor to Sun Internet Messaging Server = SIMS), which runs on Linux, or Netscape Fasttrack Server, or Bynari's Insight Server, or Samsung Contact (formerly HP OpenMail). (These are all proprietary packages.)

11. Install the Win32 version of VNC Server (http://www.realvnc.com/ , free / open-source software under the GNU General Public Licence from AT&T Cambridge) on a low-end MS-Windows 9x box running without a monitor, and use VNC Client for Linux to remotely run MS-Exchange Client on the MS-Windows 9x machine. This gives robust access to all Exchange e-mail and calendar features, as you are running Microsoft's Exchange Client on MS-Windows 9x remotely.

Implementations of the open VNC protocol reportedly faster than AT&T Cambridge's are available from TightVNC, http://www.tightvnc.com/ . Please see also http://linuxmafia.com/faq/Legacy_Microsoft/vnc-and-similar.html .

12. Install Exchange Server's SMTP Connector, and run Cyrus IMAP server (open-source software) on a back-end Linux box. You can then send and retrieve mail from any Linux e-mail client that supports IMAP, including Netscape Mail.

Open-source implementations on Linux of open standards for directory support, Webmail, and group scheduling can be used, in place of MS-Exchange Server proprietary server functions, with many of the above solution frameworks (e.g., #10): OpenLDAP (http://www.openldap.org/) is commonly used for cross-platform directory services including address books, IMP (Imap webMail Program, http://www.horde.org/imp) is commonly used for Web access to e-mail systems, and Kronolith (http://www.horde.org/kronolith/) will eventially be usable for group scheduling. Much of this work is being performed by the Horde Project (http://www.horde.org/) .

The OpenFlock Project (http://www.openflock.org/) likewise aims to do scheduling using all open-source software, in this case using GCTP protocols (but now appears abandoned).

Constructing a Linux groupware client with functionality fully comparable to that of MS-Outlook does not, contrary to many people's impressions, merely require supporting Microsoft's well-documented MAPI (Mail Application Programming Interface) protocol, but also either the MS-Exchange Server RPC-based communications protocol or the earlier and less full-featured Microsoft Mail (file-based) communications protocol. Neither is documented outside Microsoft Corporation (except that Bynari Corporation appears to have reverse-engineered them for its Insight client software).