I'm using Mozilla Thunderbird as my email client. This morning I received a message from Jim Jacobs, a regular correspondent of mine. His message was in response to a message I sent him 11/25/2007, 8:49 am. His message was dated 11/25/2007, 5:45 pm. His message is not visible in my Inbox unless I type some part of his name in the Thunderbird "Subject or Sender" text box. The only reason I caught it is that it was briefly visible right after it downloaded. There are only 239 messages total in my Inbox. I have never experienced this before. There have been no recent changes to my configuration. It's very likely that there have been recent changes to Jim Jacobs' configuration, but this behavior still seems quite bizarre. Makes me wonder how many other emails I might have missed. Any ideas?