I am using ZCS 5.0.11 NE and my users retrieve their mails using Thunderbird/IMAP. Here's a strange one... One of my users received a new mail yesterday that keeps getting marked as unread. When that particular message is highlighted in Thunderbird, it gets marked as read until another message is highlighted it gets unread. I am wondering if it's a Zimbra or Thunderbird-related problem. I looked at mailbox.log and didn't see any error whatsoever.

Anyone ever experienced a such thing?