With both Quick Filter and Global search, I enter a simple one word search string "PMD". The result is over 200 messages but I expect much fewer. I look at the messages found but don't see the PMD anywhere. I use the Find in this message and see that PMD does not occur in most of the messages found. I searched for others with this problem and found posts going back over 10 years and not all of them were answered or solved. I started to get a little suspicious so I looked at the Inbox file using Notepad++. As I suspected, I found many cases of PMD appearing in a base64 stream. To further test my theory, I made a copy of the Inbox and cut it down to just two messages. One message actually has PMD in the message and one message has PMD inside a base64 stream. Quick Filter found PMD in both messages but of course PMD is not part of the text in the second message. I am hoping that the programmers will recognize this as a bug and fix Thunderbird so that it does not search inside a base64 stream or at least provide a setting to disable searching inside a base64 stream. Thanks to the programmers for all you do. Thunderbird is my favorite e-mail client for many years.