User-Agent: Mozilla/5.0 (Windows; U; Windows NT 5.1; en-GB; rv:188.8.131.52) Gecko/20100722 Firefox/3.6.8 (.NET CLR 3.5.30729) Build Identifier: Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:184.108.40.206) Gecko/20100802 Thunderbird/3.1.2 Earlier I reported this https://bugzilla.mozilla.org/show_bug.cgi?id=577556, but this happened again and now the read column is not even visible. Reproducible: Sometimes Steps to Reproduce: 1. Clicked message from list (IMAP) 2. Pressed Delete key 3. Pressed Arrow down key Next message was selected and marked as read. More cursor up/down key pressed and messages got marked as read. After awhile it stopped happening anymore. --- Another try: 1. Locate message that is HTML based and has link 2. Click HTML message in the list 3. Click the link in the preview -> launches firefox 4. Immediately start clicking messages in the message list which might get marked as read I could reproduce that 5 times in a row, but then it did not happen.