Thunderbird has an option in "Account Settings / Composition and Addressing" labelled "Automatically quote the original message when replying", which controls the placement of "what I am replying to" and "my signature". Unfortunately, if I have copied some text from some part of what I am replying to for use elsewhere (likely not in Thunderbird at all) when I hit reply, instead of the whole original message being included, only the text I had previously copied is. I suspect that https://bugzilla.mozilla.org/show_bug.cgi?id=23394 might be related ("Opened 23 years ago Closed 14 years ago"!). My recollection is that there was, in some previous Thunderbird UI that has since been "refreshed" to beyond the point of user confusion, some way of disabling this "feature" and making "Automatically quote the original message when replying" always do what it promises to, but maybe I'm mistaken. PS: Please let's not get into the top-posting vs bottom-posting discussion here, despite how much fun it is to read some of the "Why top-posting is bad" messages from 2004. Both have their place, depending on the context, and in some contexts when replying to a message I'd be expected to include the entire previous email trail.