It appears that the indent/unindent button in the message composer doesn't indent and unindent, it increases and decreases the blockquote level. Quoting and indenting are different operations, and need to be formatted differently. I see that pressing the indent button uses a < blockquote> while "real" quoting uses < blockquote type=cite>. You would think it possible to add CSS to properly differentiate between the two. Unfortunately email clients like Gmail and Outlook don't support attribute selectors in CSS. That means that it's impossible for the recipients using Gmail and Outlook to differentiate between quotes and indents. Composing emails that don't render properly on Gmail and Outlook is just not a practical option. Very few (probably none) of the people to which I send emails are running Thunderbird. I need quote and indent to work with recipients that aren't running Thunderbird. According to multiple sources I've found, the blockquote tag has been frowned upon for a long, long time when what you want is indent. The proper way to indent is < div style="pad-left: 3em" > or < div style="left-margin: 3m" >. Would it be possible to fix the indent button so that it doesn't quote the selected text, it indents it?