Kerio Mail Transfer I had a small Linux server running Kerio at a local customer. The server had been put in quite a few years back; it didn't have a lot of disk space and it wasn't exactly a blazing performer in any sense.
You lose one now and then I lost a Kerio MailServer customer this week. They had used the software for a few years but when we sent the renewal offer for this year, it was returned marked "Cancel". I sent email to my contact at the company. That bounced, so he's likely moved on to another company.
Kerio Configuration Kerio offers a 30 day full featured demo you can download from http://www.kerio.com/kms_download.html. You can install that on Windows, Linux or Mac OS X.