I have been a WordPress user for about 6 years and have downloaded and installed hundreds of free plugins. Most of the time they work fine but occasionally you get one that has problems and if there is not an alternative then you've got to hope their support (if any) is decent. Most of the time there is no support or it is suspect at best.
That's not the case with InstaEmail! I had no problems with the plugin functioning perfectly, the only issue was the plugins lack of responsiveness on a responsive website. Now please note the plugin does not mention it is compatible with a responsive website so there should be no expectation that it is and rightfully so. However I thought it was worth at least an email to their support to see if they would respond with at least how I could edit the plugin to fix the responsive issue.
They did much more than that! They took the time to fix the issue and were very prompt in replying to all emails. I can't recommend this plugin highly enough. By offering their plugin for free InstaEmail could easily not support it but they chose the opposite and in my book that speaks volume to their character!