Not only is their product good, but their service is first rate.<p>I was recently working with the developer of the ASynK contact synchronisation tool ( <a href="http:&#x2F;&#x2F;asynk.io&#x2F;" rel="nofollow">http:&#x2F;&#x2F;asynk.io&#x2F;</a> ) to track down an issue I was having synchronising contact details from Fastmail using CardDAV.<p>It turned out to be a Fastmail issue; one of their developers was quickly on the GitHub issue chatting to the ASynK maintainer about it, and they had a fix in a couple of weeks.<p>Impressively clueful support.