I like to use keyboard shortcuts. When I send an email in ZCS, I use CTRL-Return key. The email sends but also opens the Firefox Downloader.
Also, the sound notifier for incoming email or other items takes the focus away from the window one is accessing. So, right now, using FF 3.x in WinXPPro, I have multiple tabs open with my Zimbra account and this forum that I am writing to you in. A new email came in, I got the tone and I could not write anymore until I clicked back in this text editor.