Thunderbird renders some Web pages within itself instead of sending the URI to the user's preferred default browser. This means that the user's tailoring of browser preferences (e.g., fonts, colors, link behavior with respect to tabs and windows) and installed browser extensions are not used. Plugins enabled for the browser but not for Thunderbird are also not used. There should be an option -- with a UI -- to cause all Web pages to render in the default browser. By "all Web pages", I include Web pages that are supplied via RSS feeds.
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