I've seen this behavior pretty much since we moved to Zimbra, but my inferior searching skills have been unable to find any information about it being an existing known issue or maybe even fixed.
A lot of times in the web client, if you're trying to quickly delete a bunch of messages by just mashing the delete key, it will delete a new e-mail. Heres what I think happens:
You click on the top e-mail in your inbox, and hit delete. It deletes the message and moves down to the next message. You hit delete on that one, and at the same time a new e-mail has come in to your mailbox. Once you hit delete on the 2nd messagew, it causes your inbox to refresh and the new e-mail comes in and is automatically highlighted. So then you press delete a 3rd time thinking it will delete the 3rd already read message, but instead it deletes the new e-mail you just received. You can imagine when hitting delete 3 times quick that you may barely notice that message come in and be deleted.
Anyone know of a bug for this or if it's not present in 6.0? we're still on 5.0.21