PrettyBlockquote 1.4
by Petty
The add-on ensures that the quoted text in your reply is clearly highlighted with a vertical blue line, even when viewed by recipients using different email clients like Gmail or macOS, by using inline CSS on the blockquote HTML tag.
About this Add-on
After you send the reply, many of the recipients will not see the vertical line if they are not using Thunderbird.
This extension sets the style of the blockquote using inline CSS, which is the standard that most email clients will render correctly.