Practically Replacing Microsoft Exchange Server – A 3 Part Series – 3 of 3 – Kerio Mailserver

For the first two parts of this review series, please view the following links:

Practically Replacing Microsoft Exchange Server – A 3 Part Series – 1 of 3

Practically Replacing Microsoft Exchange Server – A 3 Part Series – 2 of 3 – Zimbra Collaboration Suite

Kerio MailServer 6.5 – The Exchange Killer

Kerio MailServer, like Zimbra, has until only recently been an ‘almost but not quite’ Exchange alternative. It has offered Outlook support and integration with Active Directory since 2002, but did not initially support groupware features such as calendaring and shared contacts properly until years later. It wasn’t until 2007 that Kerio began to coalesce into an alternative to Exchange — and with the release of Kerio MailServer 6.5, its transformation into an Exchange killer is complete.

I’ve saved the best for last with Kerio — I prefer it over Zimbra as an Exchange replacement for several key reasons which I’ll outline below.

Client Software Compatibility

Kerio provides connectors for Outlook 2003 and 2007 which enable those clients, previously mentioned as irreplaceable tools for office workers, to work with Kerio as if it were Exchange itself. These connectors use the HTTP/HTTPS protocol, and as such a user can fully access their public folders and the global address list while working remotely as though they were in the office. This Outlook connector is provided at no extra charge.

Mac users are able to sync to Kerio through the use of the Kerio iSync connector, also provided at no extra charge. This connector provides both addressbook and calendar sync for users of MacOS X 10.4 Tiger, and addressbook sync for Leopard users (calendar sync can be natively accomplished by Leopard’s version of iCal, so the iSync conduit is not needed for this — though it can still be used).

Kerio also supports International standards such as CalDAV, enabling clients such as Apple iCal, Mozilla Sunbird, Novell Evolution and OSAF Chandler to connect with its calendar and participate fully with Windows/Outlook users.

Like Zimbra, Kerio has a rich web UI though it’s patterned closely after that of Exchange. In addition to this, Kerio takes it a step further with full emulation of Outlook Web Access, which is of benefit to any third party tool  or application that interfaces with Exchange via this mechanism. This opens up a larger segment of the Microsoft-entwined ecosystem to Kerio switchers than any other Exchange alternative.

Mobile Devices

ActiveSync is one of the most important features of Kerio. This isn’t emulation or the implementation of similar functionality via a third party app, it’s native, true ActiveSync protocol support. That means any ActiveSync device including Palm, Windows Mobile and the iPhone can sync all their information to Kerio with “Push” (instant notification) support and GAL search.

Blackberry users are also covered – an app installed on the handheld will enable push calendar/e-mail/contact synchronization without the need for a Blackberry Enterprise Server (BES).

Support for IT Infrastructure

The most prominent reason I prefer Kerio is that, despite its complex functionality it maintains utmost simplicity for systems administrators. Backing up and restoring or redeploying a Kerio mailserver can be done effortlessly, even when changing the host operating system, simply by copying it’s store directory as well as a handful of configuration files to the new server and then starting it. Email, contact and calendar data are stored on the filesystem rather than being placed in a database or needing to be specially imported and indexed.

The Linux version of Kerio, while officially supported only under Red Hat Enterprise, can be easily deployed on any modern distribution with little effort. This is in contrast with Zimbra which requires pretty major surgery to get running on anything other than its short list of supported distributions.

Kerio integrates with both Active Directory, supporting Windows networks, and Open Directory, supporting MacOS driven networks for authentication information, relieving admins of the need to maintain a separate user database. One nice thing about Kerio is that it can join multiple Active Directories on a per-domain basis, making it possible to host multiple mailsystems and multiple Global Address Lists on a single server.

If a single server is not enough, Kerio also supports clustering, and because its Linux and OS X versions support a wide range of UNIX filesystems and filesystem abstraction mechanisms, the mail spools and stores can be placed on a wide range of possible storage systems. Scalability is no problem.

Summing up

Kerio doesn’t come in a free version as does Zimbra, but this didn’t deter me from buying it for my own personal use. The benefits vis a vis Exchange (which I was previously using for my Calendar/Contacts/Mobile sync) were too compelling to pass up.

Kerio presents itself as a drop-in Exchange replacement, requiring as little re-training on the part of users and systems administrators alike (though system administrators should always be re-training themselves, a little elegance on the software side never hurt anyone). Some research has led me to find a growing number of Hosted Microsoft Exchange providers beginning to offer Hosted Kerio as well, which is an encouraging sign that it’s being recognized for its capabilities. I hope to see Kerio, Zimbra and others continue to take the de-facto center-seat away from Exchange in as many organizations as possible.

5 thoughts on “Practically Replacing Microsoft Exchange Server – A 3 Part Series – 3 of 3 – Kerio Mailserver

  1. I won’t comment on the differences between Zimbra and Kerio’s web interface, or the fact that Zimbra’s code is 99% open source, or on the pricing, etc. Far more important (for me): In this case *without a BES* means using Notify. So not only have you got to load software onto your blackberry device instead of using its built in software, you also have to use a technology that is easily two steps down from BES. I’m happy to pay more to use a BES, for the performance it delivers. Zimbra has got BES in working beta, and that alone is enough for me to not even consider Kerio. Also, when you say that scalability is no-problem, what exactly does that mean? I manage 4832 mailboxes for a customer, can Kerio accommodate that? If so, where does Kerio top-out? If it’s tied into the OS, how does it work with SAN deployments? I haven’t noticed any major deployments of Kerio, whereas it’s clear that Zimbra can scale to tens-of-thousands and beyond. I would love to have another option to consider besides Zimbra to replace Exchange, but other than for very small deployments, I’m not sure there is one yet. Please, tell me I’m wrong.

  2. We will stick to exchange. Especially for small implementations it is working really good. But thanks for your article it is always nice to read what others are doing.

  3. Kerio integrates with Active Directory. We’re delighted with it, even in managing large numbers of mailboxes: it’s very light on resources. However, the Blackberry integration is a problem. Both NotifyLink and Astrasync have problems: NotifyLink is too expensive and too difficult to set up, and Astrasync doesn’t support folders or native BlackBerry email features like hot links.

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