First, the cost. Secondly, the limited knowledge of configuring Exchange or alternative OS/Mail server. Then lastly, shame to admit but I still am very vague on configuring DNS with A/MX pointing at home mail server, with my web hosted with a web hosting company.
I have found Zimbra, and Open-Xchange. I like the look/sound of Zimbra, especially it can be installed on MacOS X (easier to managed compare to Linux platforms). And also, they both offer connector for Outlook, so you can use Outlook as if it is connection to Exchange. full MAPI support with email, pim and calendar. With Zimbra though, you get cached mode too.
Now, other caveat here is that, to use connector for Outlook with both email collaboration servers, you will have to get them as commercial product.
Anyhow, what is everyone else's homebrew email server?
Features that I like to see happening/to use are:
* IMAP access, for Outlook and mobile. (the least)
* Webmail access.
* Simple to set up.
* Good antispam/antivirus protection.
With my current webhosting setup, I am with WebDrive and they provide IMAP which is great, but their Spam filter is somewhat poor. And their webmail interface is just "alright".
Generally, it meets 90% of my requirements, and I'm quite happy with it. But yet, I still and contented with wanting additional boost and umph.
Sounds like i'm rambling away here.
p/s: I like the 4Smartphone.net and ICONZ's OfficeOnline. I even rationalised enough to think that I can afford one or two mailbox with them, solely to get Outlook-Exchange. I even had a look at Office Live Basic, and Windows Live Domain too, sounds good but still kinda feel limited or lacked of some features that I'm already are using.