Can I keep emails as Unread on server?

[2ManyHobbies]

Hello!
I am impressed this program....except for one hangup. I can't find where it is possible, as in Outlook, to keep messages as unread on the server. This is very important as I want to use Zimbra on my netbook and laptop throughout the day, but my husband also needs to be able to pull the emails on his desktop running Outlook when he gets home from work. Is this not possible in Zimbra?

Thank you!