Pros
I have worked at IceWarp's US office for 5 years and have seen a handful of US people, some of unfortunately questionable proficiency, come and go, so I'm a pretty good person to be writing a transparent review here. Here's the 2018 situation at IceWarp, which mirrors the situation post-2014: IceWarp has a big Prague office and a small staff in the US. If you want a workplace where people aren't always peeking over your shoulder and actually give you autonomy to do your job without heaping amounts of protocol, IceWarp is a great place to work. If you need to be constantly managed in order to stay on track (and there's nothing wrong with that) IceWarp will not suit you well. At IceWarp US, having the small staff that it does, the tasks you perform on a day to day basis are often open ended and the technology and systems you use often change so you have to be flexible. You are also generally judged based on your long-term performance rather than constantly being micromanaged, so you do have to be autonomous and self-motivated to do well at IceWarp. I have found the staff at IceWarp globally, both in the US, EU, and beyond, to be easy to work with with minimal politics. 90% of the people I work with at IceWarp globally are not just coworkers my friends and I feel that IceWarp as a workplace has always genuinely cared about me. Given the relatively small size of IceWarp, especially the US office, you are not just a number to them and indeed become a very unique factor in how they run things. If you have a personal emergency, IceWarp has always been sympathetic and understanding, no rigorous protocol to take off for something within reason. The US customers of IceWarp are also generally nice and happy, even enthusiastic about the product, so they are generally pleasant to deal with. IT people (IceWarp's clientele) are generally very logical and easy to solve problems with. IceWarp's US Support staff Dan and Steve are A+++ for resolving technical questions that come up.
Cons
There are limited opportunities for advancement at IceWarp's current size and for some reason they tend to bring in outside people for upper positions (hence the employees of questionable quality sometimes.) So I wouldn't bank on any promotions at IceWarp. It's a good place to work if you're happy with the spot you hold. Europe also has different strategic mentality than the US and sometimes they come up with some questionable to outright wacky ideas, but they are usually happy to explain their logic and listen to your opinion on the matter, so it's usually tolerable. Sometimes they will roll out stuff that's a big mistake and you just have to watch it fail then move on. Mail servers in general are kind of dry so make sure you're comfortable working with non-flashy technology where its more about configuration (the IceWarp server is really good technology) and real results than enticing people with talking points from marketing. Once again if you don't like a very high degree of autonomy this might not be the best place for you.