I'm currently using Squirrelmail which I've been using for years. It works but I'm looking for something modern that my users will really like. Looking for suggestions. What is best for running on a Linux server?
No doubt, RoundCube is a nice webmail application and its popular because of its interface. I personally use Squirrel mail as its faster and there are hundreds of squirrel mail skins available that you can install to give a nice look to squirrel mail.