I didn't want to offend anyone, I just stated my opinion on a feature I find is poorly implemented.
Here us why:
1. By definition, the message base is supposed to hold messages. Every mail client I know makes sure the message base is always intact. Of course, you as a user can break it, e.g. you can delete the attachment of a received message, but that is your responsibility.
2. In contrast, Thunderbird willfully breaks message integrity: it adds messages to the message base that are not intact messages, just pointers if you like. But these don't belong in a message base. I wonder how they'd show up in an exported message base if you don't fully fetch them.
3. Thunderbird's method facilitates user mistakes: it is easy to forget to fully fetch those messages. You may just close the program, and the message list won't warn you about it.
As for the comparison with KMail:
1. KMail's message base is always intact: it either has a message, or it doesn't. When you check your message list, you can be sure that any message you see is actually in your Inbox. All of it
2. After fetching the headers, KMail offers you to fetch the messages now, later, or not at all. Thunderbird's method is equivalent to offering option 2 only.
3. Once KMail has fetched the headers, it immediately requires user input about what to do with them. If you choose Fetch Later and then forget to, these messages won't show up in your message list, so you won't be led to believe you have them.
Andy, you have made over 1100 posts here. An old hand like you shouldn't quit in a huff over a single post you don't like