get a copy at getthunderbird.com and install it.

Where did you download Thunderbird from? as a Release channel build will never update to a Daily channel build. If you see a version with a1 on end then it was a Daily build of Thunderbird and not a Release.

Thanks for your replies.

I'm using Fedora 28 and the Thunderbird update was installed as a regular update from the Fedora System repository. thunderbird-60.0-1.fc28.x86_64 It is identified as beta software and as a "Daily" update.

I downloaded thunderbird 60.0 for linux from getthunderbird.com as : thunderbird-60.0.tar.bz2 It is identified as a standard stable version.

Apparently, this is an error with the file being distributed from the Fedora System repository.

Thanks again for your help.

> It is identified as beta software and as a "Daily" update.

You are probably looking at the Thunderbird start page. That start page will show "daily" when the server hosting this page doesn't recognize the version string,in the start page URL that Thunderbird sent.

But that is of course misleading if you actually have for example 60.0 or 60.0b10 installed.