Four actually, but one of them doesn't count.

• The title says "About Mozilla Thunderbird"
• The text says "Thunderbird is designed by Mozilla …"
• The trademark notice says "Mozilla Thunderbird and the Thunderbird logos are trademarks of the Mozilla Foundation." The MoFo part is true, I think.

What's the bug? All those seem correct.

From bug 1577638:

While we are still using "Mozilla Thunderbird" and similar phrasing in several locations, it has been slowly dying out, including on our new website. We should continue to further unify our messaging with more consistent naming as much as possible, and we shouldn't let the fact that we use mozilla services (and may need to use "mozilla thunderbird" for licensing and other legal reasons in some places) to stop that progress.

(In reply to Geoff Lankow (:darktrojan) from comment #0)

Four actually, but one of them doesn't count.

• The title says "About Mozilla Thunderbird"

Dialog title of beta on Mac is simply "Thunderbird". Are you looking at a daily or release version?

• The text says "Thunderbird is designed by Mozilla …"

True at one time. But "IS" is clearly no longer true. Should we not indicate the current state?

• The trademark notice says "Mozilla Thunderbird and the Thunderbird logos are trademarks of the Mozilla Foundation." The MoFo part is true, I think.

Correct.

Which brings up an interesting point - trademarks must be identified in order to be defended. And generally speaking trademarks must be defended in order to continue to hold them. https://www.legalzoom.com/articles/the-5-things-you-must-do-to-protect-your-trademark

On Windows it says "Mozilla Thunderbird" in the title and in the start menu.

(In reply to Richard Marti (:Paenglab) from comment #4)

On Windows it says "Mozilla Thunderbird" in the title and in the start menu.

Confirmed on Windows 10.