I've been using Zimbra Desktops for about three month, since our employer changed webmail to zimbra. One thing that bugged me from day one is the Contacts sorting. If the last name starts with a lower case like in 'de Juli' or 'van Beethoven' or you named a group with lower case, it will send it with the Z, but, not at the end of the Z but before the them, like
Young, Gregory
class 229 (this is a group)
de juli, Pierre
van Something, First
Zuiani, Marco
And in Options I could not find a way to change this!