EDIT: If you're googling this in the future, I was able to solve it by right clicking on the inbox folder and hitting 'Compact'. I guess that was able to clear up the bad data that was throwing off the indexer. Today, my inbox has gotten partially corrupted. After updating to version 128, my Thunderbird has been very sluggish. While trying to troubleshoot that, I used Properties->Repair Folder on the inbox, which is when the current problem started. In the main inbox window, everything looks fine. All emails are there, with correct subject names and correspondents, etc. Everything received before April 8 this year looks to be unaffected, but if I try to open up anything later than that, it displays a chunk of a completely different email from like 2007, with the From: and Subject: fields blank. Additionally, doing the repair marked all emails from April 21, 2008 and earlier as unread. I use POP3 to download all emails to my computer, two addresses going to the inbox. I tried using Properties->Repair Folder again, but it still leaves the same result. If I open the gigantic "Inbox" file in my Thunderbird profile folder in notepad++, scrolling down to the bottom I see the emails are still there, so they're not completely missing. In between the last good email and the first bad one, there is a huge section that starts with: --=-SgCIEz327q/2h3s2MXJ25A== Content-Type: text/plain; charset=utf-8 Content-Id: <92b40d02-593e-4a4a-8768-a31f564d0d90> Content-Transfer-Encoding: base64 and then hundreds of lines of gibberish, followed by "--=-SgCIEz327q/2h3s2MXJ25A==--" and then it goes to the next email.