MAC ADAM  The CalDav with Kerio Mail Server do not allow me create event in iCal on SnowLeopard…

I wait for a fix to switch, please update ;)

Nice Application.  
(Version 6.7.1)

KMAC99  I've been using this product for years. I recommend it to all my clients. For most of my clients I recommend they get it hosted, because then they don't have to worry about it at all, just sign up and` go. We alwayS use www.keriomailhosting.com for the hosted version of Kerio, they have the best prices and their service has been wonderful.  
(Version 6.7 patch 1)

DRFIX  I'd searched high and low for an email server that wouldn't require me to be a full time administrator. Many, while free , took too much of my time away from other tasks in order to manage or study up on, and others were so expensive as to put them out of reach of mere mortals(ex: CGP).

KMS was, for me at least, approachable and easy enough to understand that it took little time to configure a working SMTP/POP/IMAP server with options. To get the full benefit did take some time to pour over the documentation because, to be quite frank, there are some areas that simply are not explained very well or at all.

That being said I've been more than impressed by its stability and only wish that Kerio had a more liberal upgrade policy because you either get locked into their "subscription" or pay nearly the full price over and over and over. For larger enterprises I can see the benefit but for now I'll stay with an albeit "older" version but one that works.

This is a good product and I look forward to where its headed.  
(Version 6.3.1)

SWGS1  This is a replacement for Exchange, it is much more than just a mail server. Email, Contacts, Calendars, and Tasks, available anywhere with internet access. All for much cheaper than Microsoft Exchange.  
(Version 6.3)

ANONYMOUS  I have been using kerio mailserver for about 3 months now, and have been very happy with the results. The user interface is very simple, and the webmail is the first i've seen that really rivals exchange's webmail. For the price, features, and ease of use, this program is right on. The spam filter has been very good, the outlook integration is almost seamless, and the simplicity of the admin interface makes it simple to implement on any platform. Kerio's support team has been wonderful so far, walking me through any issues i had, from setup to bugfixes. I am using this with about 80 users, and they are happier with this then they were with exchange 5.  
(Version 6.1)

MARKFLO  Some of us network admins wear many hats (I wear about 5 in the small ad agency I work for) and don't have time to fiddle with confusing command-line configurations. Kerio is an enterprise-friendly e-mail solution that plays nice with Outlook and Entourage, but it costs WAY less than Exchange. Given those two points, Kerio is worth the money.

2 cents.  
(Version 6.0.9)

ANONYMOUS  world is full of free mail servers:

postfix, exim, sendmail etc etc etc

many are robost enough for busy webhosts and complex organizations

why would you need to buy one for ?  
(Version 6.0.9)

ROGIER  I have used Kerio mailserver 6.0.1 6.0.2 6.0.3 and 6.0.4. Since 6.0.3 I had the problem that reminders don't come up in Outlook xp and Outlook 2003. This problem should be fixed in 6.0.4 but it was not. This version of kerio is still buggy. don't use it for large scale networks. Use it up to 3 users. Any more go for a proffesional sollution like exchange.   
(Version 6.0.4)

ANONYMOUS  I have been using this for about 4 days. I have had nothing but problems with the mail server. The tech people are very useless and have not got a clue about what mac user want and except. Program looks nice before you install it. Then it shows its true colors . very buggy, out dated interface. Pop3 is not working for me, had to restart the machine 3 times due to a kernal panics. Only after installing this mail server. Lost a lot of time before getting it working. Worst thing is that I could not get anyone at tech support to help. Well I did not buy it so I can not say but first impression is not good. I would say if you are looking for something really great buy Staker. CGP. It rocks!  
(Version 6.0.1)

CHAD MANGEL  I've been using 5.7 for a while now and it has been bullet proof running on a Redhat 9 server. I just installed version 6 on a test server and I'm blown away. The web interface is absolutely awesome! Thus far I haven't found any major bugs. Just make sure you turn your popup blocker off for your server address. I've also found that Mozilla works the best with the new interface. This thing blows my old Exchange server away! Give me iCal support on the server side via WebDav, and this mailserver will be perfect for every platform out there!  
(Version 6.0)