I want to use Kolab as a private person, just as a platform for keeping all my contacts, events, tasks and mail together. It's because it's the only product that supports synchronizing mail+contacts+events+tasks with Thunderbird/Lightning, Win Mobile and Android (what I'm using) as well as Outlook etc.
The problem is I don't want to host it on my own, because I'm going to be forced to think about security, my incoming traffic will be overblown with hackers attempts to spamize the machine. Also, if my computer will be off for a minute (that happens frequently enough due to the ISP maintenance), I can lose an important mail.
And AFAIK there is not available Kolab web hosting, just enterprise services.
What if I install Kolab server on my home server, then link it somehow with an external mail server? Kolab will not be allowed to send e-mails, just to synchronize them with the other server, which is safer. And the external server uptime is a hoster pain, not mine.
So, how to make my internal IMAP-based mail server synchronize with an external mail-server? I need only e-mail synchronizing.